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CONTENTS. 


CIIArTEE  I. 


Drosera  rotundifolia,  or  tue  Common  Sun-dew. 

NiiimbGr  of  insects  captured  — Description  of  the  leaves  and 
their  appendages  or  tentacles  — Preliminary  sketch  of  tho>» 
action  of  the  various  parts,  and  of  the  manner  in  which 
insects  are  captured  — Duration  of  the  inflection  of  the 
tentacles  — Nature  of  the  secretion  — Manner  in  which 
insects  are  carried  to  the  centre  of  the  leaf  — Evidence  that  ' 
the  glands  have  the  power  of  absorption  — Small  size  of 
the  roots Pages  1-18 


CHAPTER  IL 


Tue  Movements  of  the  Tentacles  from  the  Contact  of 
Solid  Todies. 

Inflection  of  the  exterior  tentacles  owing  to  the  glands  of  the 
disc  being  excited  by  repeated  touches,  or  by  objects  left  in 
contact  with  them  — Difference  in  the  action  of  bodies  yield- 
ing and  not  yielding  soluble  nitrogenous  matter  — Inflection 
of  the  exterior  tentacles  directly  caused  by  objects  left  in 
contact  'with  their  glands  — Periods  of  commencing  inflection 
and  of  subsequent  re-expansion  — Extreme  minuteness  of 
the  particles  causing  inflection — Action  under  water  — 
Inflection  of  the  exterior  tentacles  when  tlieir  glands  are 
excited  by  repeated  touches  — Falling  drops  of  water  do  not 
cause  inflection 19-37 


VI 


CONTENTS 


Aggregation  of  the  Protoplasm  within  the  Cells  of  the 
Tentacles. 

Nature  of  the  contents  of  the  cells  before  aggregation  — Various 
causes  which  excite  aggregation  — The  process  commences 
within  the  glands  and  travels  down  the  tentacles  — Descrip- 
tion of  the  aggregated  masses  and  of  their  spontaneous 
movements  — Currents  of  protoplasm  along  the  walls  of  the 
cells  — Action  of  carbonate  of  ammonia  — The  granules  in 
the  protoplasm  which  flows  along  the  walls  coalesce  with  the 
central  masses  — Minuteness  of  the  quantity  of  carbonate  of 
ammonia  causing  aggregation  — Action  of  other  salts  of 
ammonia — Of  other  substances,  organic  fluids,  &c. — Of 
water  — Of  heat  — Eedissolution  of  the  aggregated  masses  — 
Proximate  causes  of  the  aggregation  of  the  protoplasm  — 
Summary  and  concluding  remarks  — Supplementary  observa- 
tions on  aggregation  in  the  roots  of  plants  . . Pages  33-65 

CHAPTER  IV. 

The  Effects  of  Heat  on  the  Leaves. 

Nature  of  the  experiments  — Effects  of  boiling  water  — Warm 
water  causes  rapid  inflection  — Water  at  a higher  tempera- 
ture does  not  cause  immediate  inflection,  but  does  not  kill 
the  leaves,  as  shown  by  their  subsequent  re-expansion  and 
by  the  aggregation  of  the  protoplasm  — A still  higher 
temperature  kills  the  leaves  and  coagulates  the  albuminous 
contents  of  the  glands 66-75 

CIIAPTEU  V. 

The  Effects  of  Non-nitrogenous  and  Nitrogenous 
Organic  Fluids  on  the  Leaves. 

Non-nitrogenous  fluids  — Solutions  of  gum  arabic  — Sugar  — 
Starch  — Diluted  alcohol — Olive  oil  — Infusion  and  decoc- 
tion of  tea  — Nitrogenous  fluids  — Milk  — Urine  — Liquid 
albumen  — Infusion  of  raw  meat  — Impure  mucus  — Saliva 
— Solution  of  isinglass  — Difference  in  the  action  of  these 
two  sets  of  fluids  — Decoction  of  green  peas -r- Decoction 
and  infusion  of  cabbage  — Decoction  of  gi'ass  leaves  76-84 


CONTENTS. 

CHAPTER  VI. 

The  Digestive  Power  of  the  SecretiOx^  op  DroseraI"^ 

The  secretion  rendered  acid  by  the  direct  and  indirect  excite- 
ment of  the  glands  — Nature  of  the  acid  — Digestible 
substances  — Albumen,  its  digestion  arrested  by  alkalies, 
recommences  by  the  addition  of  an  acid  — Meat  — Fibrin 
Syntonin  — Areolar  tissue  — Cartilage  — Fibro-cartilago  — 
Bone  — Enamel  and  dentine  — Phosphate  of  lime  — Fibrous 
basis  of  bone  — Gelatine  — Chondrin  — Milk,  casein  and 
cheese — Gluten  — Legumin  — Pollen — Globulin — Haematin 
— Indigestible  substances  — Epidermic  productions  — Fibro- 
elastic  tissue  Mucin — Pepsin — Urea  — Chiiine  — Cellulose 
— Gun-cotton— Chlorophyll  — Fat  and  oil  — Starch  — Action 
of  the  secretion  on  living  seeds  — Summary  and  concluding 
remarks  ..  ..  Pages  85-135 

CHAPTER  VII. 

The  Effects  op  Salts  op  Ammonia. 

Manner  of  performing  the  experiments  — Action  of  distilled 
water  in  comparison  with  the  solutions  — Carbonate  of 
ammonia,  absorbed  by  the  roots  — The  vapour  absorbed  by 
the  glands  Drops  on  the  disc  — Minute  drops  applied  to 
separate  glands — -Leaves  immersed  in  weak  solutions  — 
Minuteness  of  the  doses  which  induco.  aggregation  of  the 
protoplasm  — Nitrate  of  ammonia,  analogous  experiments 
with  — Phosphate  of  ammonia,  analogous  experiments  with 
— Other  salts  of  ammonia  • — Summary  and  concluding 
remarks  on  the  action  of  salts  of  ammonia  ,,  136-173-^* 

CHAPTER  Vllle 

The  Effects  op  various  other  Salts,  and  Acids,  on  the 
Leaves. 

Salts  of  sodium,  potassium,  and  other  alkaline,  earthy,  and 
metallic  salts  — Summary  on  the  action  of  these  salts  — 
Various  acids  — Summary  on  their  action  ..  ..  174-198 


vii 


vm 


CONTENTS. 


CHAPTER  IX. 


The  Effects  op  certain  Alkaloid  Poisons,  other 
n Substances  and  Vapours. 

Strychnine,  salts  of  — Quinine,  sulphate  of,  does  not  soon 
arrest  the  movement  of  the  protoplasm Other  salts  of 
quinine  — Digitaline  — • Nicotine  — Atropine  — Veratrine  — 
Colchicine  — Theine  — Curare  — Morphia  — Hyoscyamus  — 
_ Poison  of  the  cobra,  apparently  accelerates  the  movements 
of  the  protoplasm  — Camphor,  a powerful  stimulant,  its 
vapour  narcotic  — Certain  essential  oils  excite  movement  — 
Glycerine  — Water  and  certain  solutions  retard  or  prevent 
the  subsequent  action  of  phosphate  of  ammonia — Alcohol 
innocuous,  its  vapour  narcotic  and  poisonous — Chloroform, 
sulphuric  and  nitric  ether,  their  stimulant,  poisonous,  and 
narcotic  power  — Carbonic  acid  narcotic,  not  quickly 
poisonous  — Concluding  remarks  ..  ..  Pages  199-228 


CHAPTER  X. 


On  the  Sensitiveness  op  the  Leaves,  and  on  the  Lines 
OF  Transmission  op  the  Motor  Impulse. 

Glands  and  summits  of  the  tentacles  alone  sensitive  — Trans- 
mission of  the  motor  impulse  down  the  pedicels  of  the 
tentacles,  and  across  the  blade  of  the  leaf — Aggregation  of 
the  protoplasm,  a reflex  action  — First  discharge  of  the 
motor  impulse  sudden  Direction  of  the  movements  of  the 
tentacles  — Motor  impulse  transmitted  through  the  cellular 
tissue  — - Mechanism  of  the  movements  — Nature  of  the 
motor  impulse  — Re-expansion  of  the  tentacles  ..  229-261 


Recapitulation  op  the  Chiep  Observations  on 
Drosera  rotundifolia. 


262-277 


CONTENTS. 


IX 


CHAPTER  XIL  f: 

On  the  Structure  and  Movements  of  some  otheiv^ 
Species  op  Drosera. 

Drosera  anglica — Drosera  intermedia — Drosera  capensis— Drosera 
spathulata  — Drosera  filiformis  — Drosera  hinata — Concluding 
remarks  Pages  278-285’ 

^HAPTEE  XIII. _ 

Dion^a  muscipula. 

structure  of  the  leaves  — Sensitiveness  of  the  filaments  — Rapid 
movement  of  the  lobes  caused  by  irritation  of  the  filaments — 
Glands,  their  power  of  secretion— Slow  movement  caused  by 
the  absorption  of  animal  matter  — Evidence  of  absorption 
from  the  aggregated  condition  of  the  glands  — Digestive 
power  of  the  secretion  — Action  of  chloroform,  ether,  and 
hydrocyanic  acid — The  manner  in  which  insects  are  captured 
— Use  of  the  marginal  spikes  — Kinds  of  insects  captured  — 
The  transmission  of  the  motor  impulse  and  mechanism  of 
the  movements  — Re-expansion  of  the  lobes  ..  286-320 

CUAPTER  XIV. 

AlDRO  VANDA  VESICULOSA. 

Captures  crustaceans  — Structure  of  the  leaves  in  comparison 
with  those  of  Dionsea — Absorption  by  the  glands,  by  the 
quadrifid  processes,  and  points  on  the  infolded  margins  — 
Aldrovanda  vesiculosa^  ‘var.  australis  — Captures  prey  — 
Absorption  of  animal  matter  — Aldrovanda  vesiculosa^  var. 
verticillata  — Concluding  remarks 321-381 

CHAPTER  XV. 

Dkosophyllum  — Roridula  — Byblis  — Glandular  Hairs 
OTHER  Plants — Concluding  Remarks  on  the  Droserace^. 

Drosophyllum — Structure  o*^  leaves — Nature  of  the  secretion — 
Manner  of  catching  ins  ( ts — Power  of  absorption—  Digestion 
of  animal  substances—  himmary  on  Drosophyllum — Roridula 
■ — Byblis  — Glandular  hairs  of  other  plants,  their  power  of 
absorption  — Saxifraga  -J-  Primula  — Pelargonium  — Erica — ■ 
Mirabilis  — Nicotiana  — Summary  on  glandular  hairs — Con- 
cluding remarks  on  thet' ."^^oseraceie  332-367 


CONTENTS. 


& 

CHAPTER  XVL 

~ PiNGUICULA. 

Pinguicula  vulgaris  — Structure  of  leaves  — Number  of  insects 
and  other  objects  caught — Movement  of  the  margins  of  the 
leaves  — Uses  of  this  movement  — Secretion,  digestion,  and 
absorption  — Action  of  the  secretion  on  various  animal  and 
. vegetable  substances  — The  effects  of  substances  not  con- 
taining soluble  nitrogenous  matter  on  the  glands — Pinguicula 
grandijlora  — Pinguicula  lusitanica,  catches  insects  — Move- 
ment of  the  leaves,  secretion  and  digestion  ..  Pages  368-394 

CHAPTER  XVII. 

Utricularia. 

Utricularia  neglecta  — Structure  of  the  bladder — The  uses  of  the 
several  parts  — Number  of  imprisoned  animals  — Manner  of 
capture  — The  bladders  cannot  digest  animal  matter,  but 
absorb  the  products  of  its  decay  — Experiments  on  the 
absorption  of  certain  fluids  by  the  quadrifid  processes  — 
Absorption  by  the  glands  — Summary  of  the  observation  on 
absorption  — Development  of  the  bladders  — Utricularia 
vulgaris — Utricularia  minor — Utricularia  clandestina  395-430 

CHAPTER  XVIII. 

Utricularia  (continued). 

Utricularia  montana  — Description  of  the  bladders  on  the  Sub- 
terranean rhizomes  — Prey  captured  by  the  bladders  of 
plants  under  culture  and  in  a state  of  nature  — Absorption 
by  the  quadrifid  processes  and  glands  — Tubers  serving  as 
reservoirs  for  water  — Various  other  species  of  Utricularia  — 
Polypompholyx  — Genlisea,  different  nature  of  the  trap  for 
capturing  prey  — Diversified  methods  by  which  plants  are 
nourished  ..  ..  ..  431-453 


Index 


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INSECTIVOEOUS  PLANTS 


CHAPTER  I. 

Droseba  kotundifolia,  or  the  common  Sun-dew. 

Number  of  insects  captured  — Description  of  the  leaves  and  their 
appendages  oFlentacles  — Preliminary  sketch  of  the  action  of  the 
various  parts,  and  of  the  manner  in  which  insects  are  captured  — 
Duration  of  the  inflection  of  the  tentacles  — Nature  of  the  secre- 
tion— Manner  in  which  insects  are  carried  to  the  centre  of  the 
leaf — : Evidence  that  the  glands  have  the  power  of  absorption  — 
Small  size  of  the  roots. 

During  the  summer  of  1860,  I was  surprised  by  find- 
ing how  large  a number  of  insects  were  caught  by  the 
leaves  of  the  common  sun-dew  (Drosera  rotundifolia)  on 
a heath  in  Sussex.  I had  heard  that  insects  .were  thus 
caught,  but  knew  nothing  further  on  the  subject.*  I 


* As  Dr.  Nitschke  has  given 
(‘Bot.  Zeitung,’  1860,  p.  229)  the 
bibliography  of  Drosera,  I need 
not  here  go  into  details.  Most  of 
the  notices  published  before  1860 
are  brief  and  unimportant.  The 
oldest  paper  seems  to  have  been 
one  of  the  most  valuable,  namely, 
by  Dr.  Roth,  in  1782.  There  is 
also  an  interesting  though  short 
account  of  the  habits  of  Drosera  by 
Dr.  Milde,  in  the  ‘ Bot.  Zeitung,* 
1852,  p.. 510.  In  1855,  in  the ‘An- 
nales  des  So.  nat.  bot.’  tom.  iii.  pp. 
297  and  801,  MM.  Greenland  and 
Trecul  each  published  papers,  with 
figures,  on  the  structure  of  the 


leaves;  but  M.  Trecul  went  so 
far  as  to  doubt  whether  they  pos- 
sessed any  power  of  movement. 
Dr.  Nitschke’s  papers  in  the  ‘ Bot. 
Zeitung’  for  1860  and  1861  are 
by  far  the  most  important  ones 
which  have  been  published,  both 
on  the  habits  and  structure  of 
this  plant ; and  I shall  frequently 
liave  occasion  to  quote  from 
tliem.  His  discussions  on  several 
points,  for  instance  on  the  trans- 
mission of  an  excitement  from  one 
part  of  the  leaf  to  another,  are 
excellent.  On  Dec.  11, 1862,  Mr. 
J.  Scott  read  a paper  before  the 
Botanical  Society  of  Edinburgh, 


2 DROSERA  ROTUNDIFOLIA.  CiUP.  1. 

gattered  by  chance  a dozen  plants,  bearing  fifty-six 
_fully  expanded  leaves,  and  on  thirty-one  of  these  dead 
_insect^or  remnants  of  them  adhered ; and,  no  doubt, 
many  niore  would  have  been  caught  afterwards  by  these  . 
same  leaves,  and  still  more  by  those  as  yet  not  ex- 
panded. On  one  plant  all  six  leaves  had  caught  their 
prey;  and  on  several  plants  very  many  leaves  had_ 
caught  more  than  a single  insect.  On  one  large  leaf 
I - found  the  remains  of  thirteen  distinct  insects. 
Flies  (Diptera)  are  capthred  much  oftener  than  other 
/ insects.  The  largest  kind  which  I have  seen  caught 
was  a small  butterfly  {Gwnonympha  pamphilus) ; but 
the  Eev.  H.  M.  Wilkinson  informs  me  that  he  found  a 
large  living  dragon-fly  with  its  body  firmly  held  by 
^wo  leaves.  As  this  plant  is  extremely  common  in 
some  districts,  the  number  of  insects  thus  annually 
slaughtered  must  be  prodigious.  Many  plants  cause 
the  death  of  insects,  for  instance  the'^sIiCky  buds  of 
the  horse-chestnut  (jEseuly^s  Jiippocastanum),  without 
thereby  receiving,  as  far  as  We  can  perceive,  any  ad- 
vantage; but  it  was  soon  evident  that  Drosera  was 


which  was  published  in  the  Gar- 
dener’s Chronicle/  18GB,  p.  30. 
Mr.  Scott  shows  that  gentle  irrita- 
tion of  the  hairs,  as  well  as  insects 
placed  on  the  disc  of  the  leaf, 
cause  the  hairs  to  bend  in- 
wards. Mr.  A.  W.  Bennett  also 
gave  another  interesting  account 
of  the  movements  of  the  leaves 
before  the  British  Association  for 
1873.  In  this  same  year  Dr. 
Warming  published  an  essay,  in 
which  he  describes  th  dructure 
of  the  so-called  hair  , entitled, 
“ Sur  la  Difftdence  eii  re  les  Tri- 
chomes/’  &c.,  extracti  d from  the 
proceedings  of  the  So<;.  d’llist. 
Nat.  deCopenhague.  I shall  also 
have  occasion  hereafter  to  refer 


to  a paper  by  Mrs.  Treat,  of  New' 
J ersey,  on  some  American  species 
of  Drosera.  Dr.  Burdon  Sander- 
son delivered  a lecture  on  Dioiiica, 
before  the  Royal  Institution  ("pub- 
lished  in  ‘ Nature/  June  14, 1874), 
in  ^vhich  a short  account  of  my 
observations  on  the  power  of  true 
digestion  possessed  by  Drosera 
and  Dionsea  first  appeared.  Prof. 
Asa  Gray  has  done  good  service 
by  calling  attention  to  Drosera, 
and  to  other  plants  having  similar 
habits,  in  ‘ The  Nation  ’ (1874,  pp. 
2G1  and 232), and  in  other  publica- 
tions. Dr.  Hooker,  also,  in  his 
important  address  on  Carnivorous 
Plants  (Brit.  Assoc.,  Belfast,  1874 
has. given  a history  of  the  subject^ 


CliAP.  I. 


STRUCTURE  OF  THE  LEAVES. 


3 


excellently  adapted  for  the  special  purpose  of  cq^h- 
ing  insects,  so  that  the  subject  seemed  well  worth^of 
investigation.  _ 1^! 

/The  results  have  proved  highly  remarkable’;  "the  — 
more  important  ones  being — firstly,  the  extraordinary^l^, 


Fig.  1.* 

{Drosera  rotundifolia.) 

Leaf  viewed  from  above ; enlarged  four  times, 


sensitiveness  of  the  glands  to  slight  pressure  and  to 
minute  doses  of  certain  nitrogenous  fluids,  as  shown 
by  the  movements  of  the  so-called  hairs  or  tentacles ; 


* The  drawings  of  Drosera  and  eidaria,  by  my  son  Francis.  Thev 
Dionsea,  given  in  this  work,  were  liave  been  excellently  reproduced 

made  for  me  by  my  son  George  on  wood  by  Mr.  Cooper,  J8S 

Darwin ; those  of  Aldrovanda,  and  Strand, 
of  the  several  species  of  Utri- 


4 


DROSERA  ROTUNDIFOLIA. 


Chap.  I. 


secondly,  the  power  possessed  by  the  leaves  of  render- 
ing soluble  or  digesting  nitrogenous  substances,  and 
~ afterwards  absorbing  them;  thirdly,  the  changes 
— wHchTiake  place  within  the  cells  of  the  tentacles,  when 
-^--the~  glands  are  excited  in  various  ways. 

_/  It;^  necessary,  in  the  first  place,  to  describe  briefly 
. _ th^  plant.  It  bears  from  two  or  three  to  five  or  six 
leaves,  generally  extended  more  or  less  horizontally, 
but  sometimes  standing  vertically  upw^ards.  The  shape 
and  general  appearance  of  a leaf  is  shown,  as  seen 
from  above,  in  fig.  1,  and  as  seen  laterally,  in  fig.  2. 
The  leaves  are  commonly  a little  broader  than  long, 


but  this  was  not  the  case  in  the  one  here  figured. 
The  whole  upper  surface  is  covered  with  gland-bearing 
filaments,  or  tentacles,  as  I shall  call  them,  from  their 
manner  of  acting.  The  glands  were  counted  on  thirty- 
one  leaves,  but  many  of  these  were  of  unusually  large 
size,  and  the  average  number  was  192 ; the  greatest 
number  being  260,  and  the  least  130.  The  glands  are 
each  surrounded  by  large  drops  of  extremely  viscid 
secretion,  which,  glittering  in  the  sun,  have  given  rise 
to  the  plant’s  poetical  name  of  the  sun-dew. 

The  tentacles  on  the  central  part  of  the  leaf  or  disc  are 
short  and  stand  upright,  and  their  pedicels  are  green.  Towards 
the  margin  they  become  longer  and  longer  and  more  inclined 


Chap.  I. 


STRUCTURE  OF  THE  LEAVES. 


5 


outwards,  with  their  pedicels  of  a purple  colour.  Those  on  the 
extreme  margin  project  in  the  same  plane  with  the  leaf,  or  more 
commonly  (see  fig.  2)  are  considerably  reflexed.  A few  tentacles 
spring  from  the  base  of  the  footstalk  or  petiole,  and  these  are 
the  longest  of  all,  being  sometimes  nearly  i of  an  inch  in  length. 
On  a leaf  bearing  altogether  252  tentacles,  the  short  ones  on 
the  disc,  haying  green  pedicels,  were  in  number  to  the  longer 
submarginal  and  marginal  tentacles,  haying  purple  pedicels,  as 
nine  to  sixteen.  ^ 

A tentacle  consists  of  a thin,  straight,  hair-like  pedicel,  carry- 
ing a gland  on  the  summit.  The  pedicel  is  somewhat  flattened, 
and  is  formed  of  several  rows  of  elongated  cells,  filled  with  purple 
fluid  or  granular  matter.*  There  is,  however,  a narrow  zone 
close  beneath  the  glands  of  the  longer  tentacles,  and  a broader 
zone  near  their  bases,  of  a green  tint.  Spiral  vessels,  accom- 
panied by  simple  vascular  tissue,  branch  off  from  the  vascular 
bundles  in  the  blade  of  the  leaf,  and  run  up  all  the  tentacles 
into  the  glands. 

‘ Several  eminent  physiologists  have  discussed  the  homological 
nature  of  these  appendages  or  tentacles,  that  is,  whether  they 
ought  to  be  considered  as  hairs  (trichomes)  or  prolongations  of 
the  leaf.  Nitschke  has  shown  that  they  include  all  the  elements 
proper  to  the  blade  of  a leaf ; and  the  fact  of  their  including 
vascular  tissue  was  formerly  thought  to  prove  that  they  were 
prolongations  of  the  leaf,  but  it  is  now  known  that  vessels  some- 
times enter  true  hairs.f  The  power  of  movement  which  they 
possess  is  a strong  argument  against  their  being  viewed  as  hairs. 
The  conclusion  which  seems  to  me  the  most  probable  will  be 
given  in  Chap.  XV.,  namely  that  they  existed  primordially  as 
glandular  hairs,  or  mere  epidermic  formations,  and  that  their 
upper  part  should  still  be  so  considered ; but  that  their  lower 


* According  to  Nitschke  Bot. 
Zeitung,’  1861,  p.  224)  the  purple 
fluid  results  from  the  metamor- 
phosis of  chlorophyll.  Mr.  Sorby 
examined  the  colouring  matter 
with  the  spectroscope,  and  in- 
forms me  that  it  consists  of  the 
commonest  species  of  erythro- 
phyll,  “ which  is  often  met  with  in 
leaves  with  lovr  vitality,  and  in 
parts,  like  the  petioles,  which 
carry  on  leaf-functions  in  a very 
imperfect  manner.  All  that  can 
be  said,  therefore,  is  that  the  hairs 


(or  tentacles)  are  coloured  like 
parts  of  a leaf  w^hich  do  not  fulfil 
their  proper  office.” 

t Dr.  Nitschke  has  discussed 
this  subject  in  ‘Bot.  Zeitung,’ 
1861,  p.  241,  &c.  See  also  Dr. 
Warming  (‘  Sur  la  Difference  entre 
les  Trichomes,*  &c.,  1873),  who 
gives  references  to  various  puVdi- 
cations.  , See  also,  Greenland  and 
Tre'cul,  ‘ Annal.  des  Sc.  nat.  hot.’ 
(1th  series),  tom.  iii.  1855,  pp. 
237  and  303. 


6 


DROSERA  ROTUNDIFOLIA. 


CllAF.  I. 


Fig.  3. 

(^Drosera  rotundifolia.) 

l^ng'tudlnal  section  of  a gland  ; greatly  magnilied.  From  |)r,  Warming. 

niargiual  tentacles,  are  OYal,  and  of  nearly  uniform  size,  viz, 
about  of  an  inch  in  length.  Their  structm-e  is  remarkable, 
and  their  functions  complex,  for  they  secrete,  absorb,  and  are 
acted  on  by  various  stimulants.  They  consist  of  an  outer  layer 
of  small  polygonal  cells,  containing  purple  granular  matter  or 
fluid,  and  with  the  walls  thicker  than  those  of  the  pedicels. 


part,  which  alone  is  capable  of  movement,  consists  of  a prolon-^ 
gation  of  the  leaf ; the  spiral  vessels  being  extended  from  this 
to  the  uppermost  part.  We  shall  hereafter  see  that  the  ter- 
minal tentacles  of  the  divided  leaves  of  Roridula  are  still  in 
an  intermediate  condition. 

The  glands,  with  the  exception  of  those  borne  by  the  extreme 


Chap.  I. 


STRUCTURE  OF  THE  LEAVES. 


7 


Within  this  layer  of  cells  there  is  an  inner  one  of  differently 
shaped  ones,  likewise  filled  with  purple  fluid,  but  of  a slightly 
different  tint,  and  differently  affected  by  chloride  of  gold.  These 
two  layers  are  sometimes  well  seen  when  a gland  has  been 
crushed  or  boiled  in  caustic  potash.  According  to  Dr.  Warming, 
there  is  still  another  layer  of  much  more  elongated  cells,  as 
shown  in  the  accompanying  section  (fig.  3)  copied  from  his 
work;  but  these  cells  were  not  seen  by  Nitschke,  nor  by  me. 

In  the  centre  there  is  a group  of  elongated,  cylindrical  cells  of 
unequal  lengths,  bluntly  pointed  at  their  upper  ends,  truncated 
or  rounded  at  their  lower  ends,  closely  pressed  together,  and 
remarkable  from  being  surrounded  by  a spiral  line,  which  can  be 
separated  as  a distinct  fibre. 

These  latter  cells  are  filled  with  limpid  fluid,  which  after  long 
immersion  in  alcohol  deposits  much  brown  matter.  I presume 
that  they  are  actually  connected  with  the  spiral  vessels  which  run 
up  the  tentacles,  for  on  several  occasions  the  latter  were  seen  to 
divide  into  two  or  three  excessively  thin  branches,  which  could 
be  traced  close  up  to  the  spiriferous  cells.  Their  development 
has  been  described  by  Dr.  Warming.  Cells  of  the  same  kind 
have  been  observed  in  other  plants,  as  I hear  from  Dr.  Hooker, 
and  were  seen  by  me  in  the  margins  of  the  leaves  of  Pinguicula. 
Whatever  their  function  may  be,  they  are  not  necessary  for  the 
secretion  of  the  digestive  fluid,  or  for  absorption,  or  for  the 
communication  of  a motor  impulse  to  other  parts  of  the  leaf, 
as  we  may  infer  from  the  structure  of  the  glands  in  some  other 
genera  of  the  Droseracea3. 

The  extreme  marginal  tentacles  differ  slightly  from  the  others. 
Their  bases  are  broader,  and  besides  their  own  vessels,  they 
receive  a fine  branch  from  those  which  enter  the  tentacles 
on  each  side.  Their  glands  are  much  elongated,  and  lie  em- 
bedded on  the  upper  surface  of  the  pedicel,  instead  of  standing 
at  the  apex.  In  other  respects  they  do  not  differ  essentially 
from  the  oval  ones,  and  in  one  specimen  I found  every  possible 
transition  between  the  two  states.  In  another  specimen  there 
were  no  long-headed  glands.  These  marginal  tentacles  lose 
their  irritability  earlier  than  the  others ; and  when  a stimulus 
is  applied  to  the  centre  of  the  leaf,  they  are  excited  into  action 
after  the  others.  When  cub  >.  ‘ leaves  are  immersed  in  water, 
they  alone  often  become  inflec  ed.  i 

The  purple  fluid  or  gram  lar  matter  wliich  fills  the  cells  of 
the  glands  differs  to  a certain  extent  from  that  within  the 
cells  of  the  pedicels.  For  when  a leaf  is  placed  in  hot  water  or  in 
certain  acids,  the  glands  beconjie  quite  white  and  opaque,  whereas 


8 DROSERA  ROTUNDIFOLIA.  CiUP,  I. 

the  cells  of  the  pedicels  are  rendered  of  a bright  red,  with  tho 
exception  of  those  close  beneath  the  glands.  These  latter  cells 
lose  their  pale’  red  tint ; and  the  green  matter  which  they,  as 
well  as  the  basal  cells,  contain,  becomes  of  a brighter  green. 
The  petioles  bear  many  multicellular  hairs,  some  of  which 
near  the  blade  are  surmounted,  according  to  Nitschke,  by  a 
few  rounded  cells,  which  appear  to  be  rudimentary  glands. 
Both  surfaces  of  the  leaf,  the  pedicels  of  the  tentacles,  espe- 
cially the  lower  sides  of  the  outer  ones,  and  the  petioles,  are 
studded  with  minute  papillm  (hairs  or  trichomes),  having  a 
conical  basis,  and  bearing  on  their  summits  two,  and  occasion- 
ally three  or  even  four,  rgunded  cells,  containing  much  proto- 
plasm. These  papillae  are  generally  colourless,  but  sometimes 
include  a little  purple  fluid.  They  vary  in  development,  and 
graduate,  as  Nitschke  * states,  and  as  I repeatedly  observed 
into  the  long  multicellular  hairs.  The  latter,  as  well  as  the 
papillae,  are  probably  rudiments  of  formerly  existing  tentacles. 

I may  here  add,  in  order  not  to  recur  to  the  papillae,  that  they 
do  not  secrete,  but  are  easily  permeated  by  various  fluids : thus 
when  living  or  dead  leaves  are  immersed  in  a solution  of  one 
part  of  chloride  of  gold,  or  of  nitrate  of  silver,  to  437  of  water, 
they  are  quickly  blackened,  and  the  discoloration  soon  spreads 
to  the  surrounding  tissue.  The  long  multicellular  hairs  are 
not  so  quickly  affected.  After  a leaf  had  been  left  in  a weak 
infusion  of  raw  meat  for  10  hours,  the  cells  of  the  papillae  had 
evidently  absorbed  animal  matter,  for  instead  of  limpid  fluid 
they  now  contained  small  aggregated  masses  of  protoplasm, 
which  slowly  and  incessantly  changed  their  forms.  A similar 
result  followed  from  an  immersion  of  only  15  minutes  in  a 
solution  of  one  part  of  carbonate  of  ammonia  to  218  of  water, 
and  the  adjoining  cells  of  the  tentacles,  on  which  the  papillse 
were  seated,  now  likewise  contained  aggregated  masses  of  proto- 
plasm. We  may  therefore  conclude  that  when  a leaf  has  closely 
clasped  a captured  insect  in  the  manner  immediately  to  bo 
described,  the  papillae,  which  project  from  the  upper  surface 
of  the  leaf  and  of  the  tentacles,  probably  absorb  some  of  the 
animal  matter  dissolved  in  the  secretion ; but  this  cannot  be 
the  case  with  tho  papillm  on  tho  backs  of  the  leaves  or  on  tlia 
petioles.  


♦ Nitschke  has  elaborately  described  and  figured  tlieso  papilla), 
Bot.  Zeituug,*  1861,  pp.  284,  253,  254, 


Chap.  I. 


ACTION  OF  THE  PARTS. 


9 


Preliminary  Sketch  of  the  Action  of  the  several  Parts,  and 
of  the  Manner  in  which  Insects  are  Captured. 

^ If  a small  organic  or  inorganic  object  be  placed  on 
the  glands  in  the  centre  of  a leaf,  these  transmit  a 
motor  impulse  to  the  marginal  tentacles.  The  nearer 
ones  are  first  affected  and  slowly  bend  towards  the 
centre,  and  then  those  farther  off,  until  at  last  all 
become  closely  inflected  over  the  object.  This  takes 
place  in  from  one  hour  to  four  or  five  or  more  hours. 
The  difference  in  the  time  required  depends  on  many 
circumstances ; namely  on  the  size  of  the  object  and 
on  its  nature,  that  is,  whether  it  contains  soluble 
matter  of  the  proper  kind ; on  the  vigour  and  age  of 
the  leaf ; whether  it  has  lately  been  in  action ; and, 
according  to  Nitschke,*  on  the  temperature  of  the 
day,  as  likewise  seemed  to  me  to  be  the  case.  I A living 
insect  is  a more  efficient  object  than  a dead  one,  as 
in  struggling  it  presses  against  the  glands  of  many 
tentacles.  An  insect,  such  as  a fly,  with  thin  integu- 
ments, through  which  animal  matter  in  solution  can 
readily  pass  into  the  surrounding  dense  secretion,  is 
more  efficient  in  causing  prolonged  inflection  than  an 
insect  with  a thick  coat,  such  as  a beetle.  The  inflec- 
tion of  the  tentacles  takes  place  indifierently  in  the 
light  and  darkness;  and  the  plant  is  not  subject  to 
any  nocturnal  movement  of  so-called  sleep. 

If  the  glands  on  the  disc  are  repeatedly  touched  or 
brushed,  although  no  object  is  left  on  them,'  the 
marginal  tentacles  curve  inwards.  So  again,  if  drops 
of  various  fluids,  for  instance  of  saliva  or  of  a solu- 
tion of  any  salt  of  ammonia,  are  placed  on  the  central 
glands,  the  same  result  quickly  follows,  sometimes  in 
under  half  an  hour. 


♦ ‘Bot.  Zeitung,*  1860,  p.  216, 


10  DROSERA  ROTUNDIFOLIA.  Chap,  1. 

^ The  tentacles  in  the  act  of  inflection  sweep  through 
a wide  space ; thus  a marginal  tentacle,  extended  in 
the  same  plane  with  the  blade,  moves  through  an  angle 
of  180° ; and  I have  seen  the  much  reflected  tentacles 
of  a leaf  which  stood  upright  move  through  an  angle 
of  not  less  than  270°.  The  bending  part  is  almost 
confined  to  a short  space  near  the  base ; but  a rather 


larger  portion  of  the 


(Drosera  rotundifolia.) 

I,eaf  (enlarged)  with  all  the  tentacles 
closely  inflected,  from  immersion  in  a 
solution  of  phosphate  of  ammonia  (one 
part  to  87,500  of  water). 


elongated  exterior  tentacles 


Fig.  5. 

(Drvsera  rotundifolia.') 

Leaf  (enlarged)  with  the  tentacles  on  one 
side  inflected  over  a bit  of  meat  placed 
on  the  disc. 


becomes  slightly  incurved ; the  distal  half  in  all  cases 
remaining  straight.  The  short  tentacles  in  the  centre 
of  the  disc  when  directly  excited,  do  not  become  in- 
flected ; but  they  are  capable  of  inflection  if  excited 
by  a motor  impulse  received  from  other  glands  at  a 
distance.  Thus,  if  a leaf  is  immersed  in  an  infusion 
of  raw  meat,  or  in  a weak  solution  of  ammonia  (if  the 


Chat.  I. 


ACTION  OF  THE  PARTS. 


11 


solution  is  at  all  strong,  the  leaf  is  paralysed),  all  the 
exterior  tentacles  bend  inwards  (see  tig.  4),  excepting 
those  near  the  centre,  which  remain  upright ; but  these 
bend  towards  any  exciting  object  placed  on  one  side 
of  the  disc,  as  shown  in  tig.  5.  The  glands  in  fig.  4 
may  be  seen  to  form  a dark  ring  round  the  centre  ; and 
this  follows  from  the  exterior  tentacles  increasing  in 
length  in  due  proportion,  as  they  stand  nearer  to  the 
circumference./ 

The  kind  of  inflection  which  the  tentacles  undergo 
is  best  shown  when  the  gland  of  one  of  the  long  exterior 


CL 


{Drosera  rotundifolia.) 

Diagram  showing  one  of  the  exterior  tentacles  closely  inflected ; the  two  ad.joiniiig 
ones  in  their  ordinary  position. 

tentacles  is  in  any  way  excited ; for  the  surrounding 
ones  remain  unaffected.  In  the  accompanying  outline 
(fig.  6)  we  see  one  tentacle,  on  which  a particle  of 
meat  had  been  placed,  thus  bent  towards  the  centre  of 
the  leaf,  with  two  others  retaining  their  original 
position.  A gland  may  be  excited  by  being  simply 
touched  three  or  four  times,  or  by  prolonged  contact 
with  organic  or  inorganic  objects,  and  various  fluids.  I 
have  distinctly  seen,  through  a lens,  a tentacle  begin- 
:iing  to  bend  in  ten  seconds,  after  an  object  had  been 


12  DROSERA  ROTUNDIFOLIA.  Chap.  L ^ 

placed  on  its  gland ; and  I have  often  seen  strongly  h 
pronounced  inflection  in  under  one  minute.  It  is  sur-  ' 
prising  how  minute  a particle  of  any  substance,  such 
as  a bit  of  thread  or  hair  or  splinter  of  glass,  if  placed  j 
in  actual  contact  with  the  surface  of  a gland,  suffices  ^ 
to  cause  the  tentacle  to  bend.  If  the  object,  which  has  i! 
been  carried  by  this  movement  to  the  centre,  be  not 
very  small,  or  if  it  contains  soluble  nitrogenous  matter,  ' 
it  acts  on  the  central  glands ; and  these  transmit  a j 
motor  impulse  to  the  exterior  tentacles,  causing  them 
to  bend  inwards.  I 

Not  only  the  tentacles,  but  the  blade  of  the  leaf  I 
often,  but  by  no  means  always,  becomes  much  in-  I 
curved,  when  any  strongly  exciting  substance  or  fluid 
is  placed  on  the  disc.  Drops  of  milk  and' of  a solution 
of  nitrate  of  ammonia  or  soda  are  particularly  apt  to 
produce  this  effect.  The  blade  is  thus  converted  into 
a little  cup.  The  manner  in  which  it  bends  varies  ! 
greatly.  Sometimes  the  apex  alone,  sometimes  one 
side,  and  sometimes  both  sides,  become  incurved.  For 
instance,  I placed  bits  of  hard-boiled  egg  on  three 
leaves ; one  had  the  apex  bent  towards  the  base ; the 
second  had  both  distal  margins  much  incurved,  so  ^ 
that  it  became  almost  triangular  in  outline,  and  this 
perhaps  is  the  commonest  case  ; whilst  the  third  blade 
was  not  at  all  affected,  though  the  tentacles  were  as 
closely  inflected  as  in  the  two  previous  cases.  The 
whole  blade  also  generally  rises  or  bends  upwards,  and  • 
thus  forms  a so  aller  angle  with  the  footstalk  than  it 
did  before.  'ais  appears  at  first  sight  a |distinct  ‘ 
kind  of  move]  lent,  but  it  results  from  the  incurvation  . 
of  that  part  cfi  the  margin  which  is  attached  to  the 
footstalk,  causing  the  blade,  as  a whole,  to  curve  or 
move  upwards] 

The  lengthl  of  time  curing  which  the  tentacles  as 


1 


Ghap,  I, 


ACTION  OF  THE  PAKTS. 


13 


well  as  the  blade  remain  inflected  over  an  object  placed 
on  the  disc,  depends  on  various  circumstances ; namely 
on  the  vigour  and  age  of  the  leaf,  and,  according  to 
Dr.  Nitschke,  on  the  temperature,  for  during  cold 
weather  when  the  leaves  are  inactive,  they  re-expand 
at  an  earlier  period  than  when  the  weather  is  warm. 
But  the  nature  of  the  object  is  by  far  the  most 
important  circumstance ; I have  repeatedly  found  that 
the  tentacles  remain  clasped  for  a much  longer  average 
time  over  objects  which  yield  soluble  nitrogenous 
matter  than  over  those,  whether  organic  or  inorganic, 
which  yield  no  such  matter.  After  a period  varying 
from  one  to  seven  days,  the  tentacles  and  blade  re- 
expand, and  are  then  ready  to  act  again.  I have  seen 
the  same  leaf  inflected  three  successive  times  over 
insects  placed  on  the  disc;  and  it  would  probably 
have  acted  a greater  number  of  times. 

The  secretion  from  the  glands  is  extremely  viscid, 
so  that  it  can  be  drawn  out  into  long  threads.  It 
appears  colourless,  but  stains  little  balls  of  paper  pale 
pink.  An  object  of  any  kind  placed  on  a gland  always 
causes  it,  as  I believe,  to  secrete  more  freely ; but 
the  mere  presence  of  the  object  renders  this  difficult 
to  ascertain.  In  some  cases,  however,  the  effect  was 
strongly  marked,  as  when  particles  of  sugar  were 
added;  but  the  result  in  this  case  is  probably  due 
merely  to  exosmose.  Particles  of  carbonate  and  phos- 
phate of  ammonia  and  of  some  other  salts,  for  instance 
sulphate  of  zinc,  likewise  increase  the  secretion.  Im- 
mersion in  a solution  of  one  part  of  chloride  of  gold, 
or  of  some  other  salts,  to  437  of  water,  excites  the 
glands  to  largely  increased  secretion;  on  the 'other 
hand,  tartrate  of  antimony  produces  no  such  effect. 
Immersion  in  many  acids  (of  the  strength  of  one  part 
to  437  of  water)  likewise  causes  a wonderful  amount  of 


14  BIIOSERA  ROTUNDIFOLIA.  Chap.  I. 

I 

secretion,  so  that  when  the  leaves  are  lifted  out,  long  ’ 
ropes  of  extremely  viscid  fluid  hang  from  them.  Somo  | 
acids,  on  the  other  hand,  do  not  act  in  this  manner.  : 
Increased  secretion  is  not  necessarily  dependent  on  : 
the  inflection  of  the  tentacle,  for  particles  of  sugar  and  j 
of  sulphate  of  zinc  cause  no  movement.  |. 

It  is  a much  more  remarkable  fact  that  when  an 
object,  such  as  a bit  of  meat  or  an  insect,  is  placed  on 
the  disc  of  a leaf,  as  soon  as  the  surrounding  tentacles 
become  considerably  inflected,  their  glands  pour  forth 
an  increased  amount  of  secretion.  I ascertained  this  - 
by  selecting  leaves  with  equal-sized  drops  on  the  two 
sides,  and  by  placing  bits  of  meat  on  one  side  of  the 
disc ; and  as  soon  as  the  tentacles  on  this  side  became 
much  inflected,  but  before  the  glands  touched  the  meat, 
the  drops  of  secretion  became  larger.  This  was  re- 
peatedly observed,  but  a record  was  kept  of  only 
thirteen  cases,  in  nine  of  which  increased  secretion  was 
plainly  observed ; the  four  failures  being  due  either  to 
the  leaves  being  rather  torpid,  or  to  the  bits  of  meat 
being  too  small  to  cause  much  inflection.  We  must 
therefore  conclude  that  the  central  glands,  when 
strongly  excited,  transmit  some  influence  to  the  glands 
of  the  circumferential  tentacles,  causing  them  to  secrete 
more  copiously. 

It  is  a still  more  important  fact  (as  we  shall  see 
more  fully  when  we  treat  of  the  digestive  power  of 
the  secretion)  that  when  the  tentacles  become  inflected, 
owing  to  the  central  glands  having  been  stimulated 
mechanically,  or  by  contact  with  animal  matter,  the 
secretion  not  only  increases  in  quantity,  but  changes 
its  nature  and  becomes  acid ; and  this  occurs  before 
the  glands  have  touched  the  object  on  the  centre  of 
the  leaf.  \This  acid  is  of  a difterent  nature  from  that 
contained  in  the  tissue  of  the  leaves.  As  long  as  the 


fcilAP.  I. 


ACTION  OF  THE  PARTS. 


15 


$,eatacles  remain  closely  inflected,  tlie  glands  continue 
jfco  secrete,  and  the  secretion  is  acid ; so  that,  if  neu- 
iralised  by  carbonate  of  soda,  it  again  becomes  acid 
After  a few  hours.  / I have  observed  the  same  leaf  with 
ihe  tentacles  closely  inflected  over  rather  indigestible 
^jjUbstances,  such  as  chemically  prepared  casein,  pour- 
ijng  forth  acid  secretion  for  eight  successive  days,  and 
dver  bits  of  bone  for  ten  successive  days. 

/ The  secretion  seems  to  possess,  like  the  gastric  juice 
of  the  higher  animals,  some  antiseptic  power.f  During 
very  warm  weather  I placed  close  together  two  equal- 
sized  bits  of  raw  meat,  one  on  a leaf  of  the  Drosera, 
and  the  other  surrounded  by  wet  moss.  They  were 
thus  left  for  48  hrs.,  and  then  examined.  The  bit  on 
the  moss  swarmed  with  infusoria,  and  was  so  much 
decayed  that  the  transverse  strim  on  the  muscular 
fibres  could  no  longer  be  clearly  distinguished ; 
whilst  the  bit  on  the  leaf,  which  was  bathed  by  the 
secretion,  was  free  from  infusoria,  and  its  striaB  were 
perfectly  distinct  in  the  central  and  undissolved  por- 
tion. In  like  manner  small  cubes  of  albumen  and 
cheese  placed  on  wet  moss  became  threaded  with 
filaments  of  mould,  and  had  their  surfaces  slightly 
discoloured  and  disintegrated;  whilst  those  on  the 
leaves  of  Drosera  remained  clean,  the  albumen  being 
changed  into  transparent  fluid. 

As  soon  as  tentacles,  which  have  remained  closely 
inflected  during  several  days  over  an  object,  begin  to 
re-expand,  their  glands  secrete  less  freely,  or  cease 
to  secrete,  and  are  left  dry.  In  this  state  they  are 
covered  with  a film  of  whitish,  semi-fibrous  matter, 
which  was  held  in  solution  by  the  secretion.  J The 
drying  of  the  glands  during  the  act  of  re-expan- 
sion  is  of  some  little  service  to  the  plant ; for  I have 
often  observed  that  objects  adhering  to  the  leaves 
2 


i 

I 

16  DROSERA  ROT  UNDIFOLIA.  Chap. 

could  then  be  blown  away  by  a breath  of  air;  th|) 
leaves  being  thus  left  unencumbered  and  free  for  futurO 
action.)  Nevertheless,  it  often  happens  that  all  thb 
glands  do  not  become  completely  dry ; and  in  thi:« 
case  delicate  objects,  such  as  fragile  insects,  are  some- 
times torn  by  the  re-expansion  of  the  tentacles  into 
fragments,  which  remain  scattered  all  over  the  leaf. 
After  the  re-expansion  is  complete,  the  glands  quickly 
begin  to  re-secrete,  and  as  soon  as  fulbsized  drops 
are  formed,  the  tentacles  are  ready  to  clasp  a nevV 
object. 

When  an  insect  alights  on  the  central  disc,  it  is 
instantly  entangled  by  the  viscid  secretion,  and  the 
surrounding  tentacles  after  a time  begin  to  bend,  and 
ultimately  clasp  it  on  all  sides.  ^Insects  are  generally 
killed,  according  to  Dr.  Nitschke,  in  about  a quarter 
of  ai^  hour,  owing  to  their  tracheae  being  closed  by 
the  secretior^  If  an  insect  adheres  to  only  a few  of 
the  glands  of  the  exterior  tentacles,  these  soon 
become  inflected  and  carry  their  prey  to  the  tentacles 
next  succeeding  them  inwards;  these  then  bend  in- 
wards, and  so  onwards,  until  the  insect  is  ultimately 
carried  by  a curious  sort  of  rolling  movement  to  the 
centre  of  the  leaf.  Then,  after  an  interval,  the  ten- 
tacles on  all  sides  become  inflected  and  bathe  their 
prey  with  their  secretion,  in  the  same  manner  as 
if  the  insect  had  first  alighted  on  the  central  disc.  It 
is  surprising  how  minute  an  insect  suffices  to  cause 
this  action : for  instance,  I have  seen  one  of  the 
smallest  species  of  gnats  (Culex),  which  had  just 
settled  with  its  excessively  delicate  feet  on  the 
glands  of  the  outermost  tentacles,  and  these  were 
already  beginning  to  curve  inwards,  though  not  a 
single  gland  had  as  yet  touched  the  body  of  the 
insect.  Had  I not  interfered,  this  minute  gnat  would 


/HAP.  1. 


ACTION  OF  THE  PAKTS. 


17 


assuredly  have  been  carried  to  the  centre  of  the  leaf 
iind  been  securely  clasped  on  all  sides.  We  shall 
hereafter  see  what  excessively  small  doses  of  certain 
organic  fluids  and  saline  solutions  cause  strongly 
iinarked  inflection. 

' ^Whether  insects  alight  on  the  leaves  by  mere 
chance,  as  a resting-place,  or  are  attracted  by  the 
odour  of  the  secretion,  I know  not.  * I suspect  from 
the  number  of  insects  caught  by  the  English  species 
of  Drosera,  and  from  what  I have  observed  with  some 
exotic  species  kept  in  my  greenhouse,  that  the  odour 
is  attractive.  In  this  latter  case  the  leaves  may  be 
compared  with  a baited  trap ; in  the  former  case  with 
a trap  laid  in  a run  frequented  by  game,  but  without 
any  bait. 

^That  the  glands  possess  the  power  of  absorption,  is  " 
shown  by  their  almost  instantaneously  becoming  dark- 
coloured  when  given  a minute  quantity  of  carbonate  of 
ammonia  ; the  change  of  colour  being  chiefly  or  exclu- 
sively due  to  the  rapid  aggregation  of  their  contents.\ 
When  certain  other  fluids  are  added,  they  become  pale- 
coloured.  Their  power  of  absorption  is,  however,  best 
shown  by  the  widely  different  results  which  follow, 
from  placing  drops  of  various  nitrogenous  and  non- 
nitrogenous  fluids  of  the  same  density  on  the  glands 
of  the  disc,  or  on  a single  marginal  gland ; and  like- 
wise by  the  very  different  lengths  of  time  during  which 
the  tentacles  remain  inflected  over  objects,  which  yield 
or  do  not  yield  soluble  nitrogenous  matter.  This 
same  conclusion  might  indeed  have  been  inferred  from 
the  structure  and  moveme  ts  of  the  leaves,  which  are 
so  admirably  adapted  for  apturing  insects. 

‘I  The  absorption  of  ai  imal  matter  from  captured 
insects  explains  how  Drosera  can  flourish  in  extremely 
poor  peaty  soil, — in  some  cases  wnere  nothing  but 


18  DROSERA  ROTUNDIFOLIA.  Chap.  ^ 

sphagnum  moss  grows,  and  mosses  depend  altogethe'r 
on  the  atmosphere  for  their  nourishment.  \ Although 
the  leaves  at  a hasty  glance  do  not  appear  green,  owing 
to  the  purple  colour  of  the  tentacles,  yet  the  upper  and 
lower  surfaces  of  the  blade,  the  pedicels  of  the  central 
tentacles,  and  the  petioles  contain  chlorophyll,  so  that, 
no  doubt,  the  plant  obtains  and  assimilates  carbonic 
acid  from  the  air.  ^Nevertheless,  considering  the 
nature  of  the  soil  where  it  grows,  the  supply  of  nitrogen 
would  be  extremely  limited,  or  quite  deficient,  unless 
the  plant  had  the  power  of  obtaining  this  important 
element  from  captured  insects.  We  can  thus  under- 
stand how  it  is  that  the  roots  are  so  poorly  developed. 
These  usually  consist  of  only  two  or  three  slightly 
divided  branches,  from  half  to  one  inch  in  length, 
furnished  with  absorbent  hairs.  It  appears,  therefore, 
that  the  roots  serve  only  to  imbibe  water ; though,  no 
doubt,  they  would  absorb  nutritious  matter  if  present 
in  the  soil ; for  as  we  shall  hereafter  see,  they  absorb 
a weak  solution  of  carbonate  of  ammonia.  I A plant 
of  Drosera,  with  the  edges  of  its  leaves  curled  in- 
wards, so  as  to  form  a temporary  stomach,  with  the 
glands  of  the  closely  inflected  tentacles  pouring  forth 
their  acid  secretion,  which  dissolves  animal  matter, 
afterwards  to  be  absorbed,  may  be  said  to  feed  like  an 
animal.  But,  differently  from  an  animal,  it  drinks  by 
means  of  its  roots ; and  it  must  drink  largely,  so  as  to 
retain  many  drops  of  viscid  fluid  round  the  glands, 
sometimes  as  many  as  260,  exposed  during  the  whole 
day  to  a glaring  sun. 


0/UP.n.  INFLECTION  INDIRECTLY  CAUSED. 


19 


CHAPTEE  II. 

The  Movements  of  the  Tentacles  from  the  Contact  of  Solid 
Bodies. 

Taflection  of  the  exterior  tentacles  owing  to  the  glands  of  the  disc 
being  excited  by  repeated  touches,  or  by  objects  left  in  contact 
with  them  — Difference  in  the  action  of  bodies  yielding  and  not 
yielding  soluble  nitrogenous  matter  — Inflection  of  the  exterior 
tentacles  directly  caused  by  objects  left  in  contact  with  their 
glands-  Periods  of  commencing  inflection  and  of  subsequent  re- 
expansion — Extreme  minuteness  of  the  particles  causing  inflection 
— Action  under  water— Inflection  of  the  exterior  tentacles  when 
their  glands  are  excited  by  repeated  touches  — Falling  drops  of 
water  do  not  cause  inflection. 

t WILL  give  in  this  and  the  following  chapters  some  of 
the  many  experiments  made,  which  best  illustrate  the 
manner  and  rate  of  movement  of  the  tentacles,  when 
excited  in  various  ways.  /The  glands  alone  in  all 
ordinary  cases  are  susceptible  to  excitement.  When 
excited,  they  do  not  themselves  move  or  change  form, 
but  transmit  a motor  impulse  to  the  bending  part  of 
their  oum  and  adjoining  tentacles,  and  are  thus  carried 
towards  the  centre  of  the  leaf.  / Strictly  speaking,  the 
glands  ought  to  be  called  irritable,  as  the  term  sensi- 
tive generally  implies  consciousness ; but  no  one  sup- 
poses that  the  Sensitive-plant  is  conscious,  and  as  I 
ha\e  found  the  term  convenient,  I shall  use  it  without 
scruple.  I will  commence  with  the  movements  of  the 
exterior  tentacles,  when  indirectly  excited  by  stimulants 
applied  to  the  glands  of  the  short  tentacles  on  the  disc. 
The  exterior  tentacles  may  be  said  in  this  case  to  be 
indirectly  excited,  because  their  own  glands  are  not 
directly  acted  on.  / The  stimulus  proceeding  from  the 
glands  ot  the  disc  acts  on  the  bending  part  of  the 


20 


DROSERA  ROTUNDI  ^OLIA, 


Chap.  JL, 


exterior  tentacles,  near  their  bases,  and  does  not  (us 
will  hereafter  be  proved)  first  travel  up  the  pedicels  to 
the  glands,  to  be  then  reflected  back  to  the  bending 
place,  i Nevertheless,  some  influence  does  travel  up  to 
the  glands,  causing  them  to  secrete  more  copiously, 
and  the  secretion  to  become  acid.  This  latter  fact 
is,  I believe,  quite  new  in  the  physiology  of  plants ; 
it  has  indeed  only  recently  been  established  that  in 
the  animal  kingdom  an  influence  can  be  transmitted 
along  the  nerves  to  glands,  modifying  their  power  of 
secretion,  independently  of  the  state  of  the  blood- 
vessels. 

The  Inflection  of  the  Exterior  Tentacles  from  the  Glands 

of  the  Disc  being  excited  by  Bejoeated  Touches,  or  by 

Objects  left  in  Contact  with  them. 

The  central  glands  of  a leaf  were  irritated  with  a 
small  stiff  camel-hair  brush,  and  in  70  m.  (minutes) 
several  of  the  outer  tentacles  were  inflected ; in  5 hrs. 
(hours)  all  the  sub-marginal  tentacles  were  inflected ; 
next  luorning  after  an  interval  of  about  22  hrs.  they  were 
fully  re-expanded.  In  all  the  following  cases  the  period 
is  reckoned  from  the  time  of  first  irritation.  Another 
leaf  treated  in  the  same  manner  had  a few  tentacles 
inflected  in  20  m. ; in  4 hrs.  all  the  submarginal  and 
some  of  the  extreme  marginal  tentacles,  as  well  as  the 
edge  of  the  leaf  itself,  were  inflected ; in  17  hrs.  they 
had  recovered  their  proper,  expanded  position.  I then 
put  a dead  fly  in  the  centre  of  the  last-mentioned  leaf, 
and  next  morning  it  was  closely  clasped ; five  days 
afterwards  the  leaf  re-expanded,  and  the  tentacles, 
with  their  glands  surrounded  by  secretion,  were  ready 
to  act  again. 

Particles  of  meat,  dead  flies,  bits  of  paper,  wood, 
dried  moss,  sponge,  cinders,  glass,  &c.,  w^ere  repeatedly 


(3hap.il  inflection  INDIRECTLY  CAUSED.  21 

placed  on  leaves,  and  these  objects  were  well  euibraced 
Sn  various  periods  from  1 hr.  to  as  long  as  24  hrs.,  and 
ijjet  free  again,  with  the  leaf  fully  re-expanded,  in  from 
(j^ne  or  two,  to  seven  or  even  ten  days,  according  to 
ihe  nature  of  the  object.  On  a leaf  which  had 
paturally  caught  two  flies,  and  therefore  had  already 
^losed  and  reopened  either  once  or  more  probably 
twice,  I put  a fresh  fly : in  7 hrs,  it  was  moderately, 
and  in  21  hrs.  thoroughly  well,  clasped,  with  the 
edges  of  the  leaf  inflected.  In  two  days  and  a 
half  the  leaf  had  nearly  re-expanded ; as  the  exciting 
object  was  an  insect,  this  unusually  short  period  of  in- 
flection was,  no  doubt,  due  to  the  leaf  having  recently 
been  in  action.  Allowing  this  same  leaf  to  rest  for 
only  a single  day,  I put  on  another  fly,  and  it  again 
closed,  but  now  very  slowly ; nevertheless,  in  less  than 
two  days  it  succeeded  in  thoroughly  clasping  the  fly. 

I When  a small  object  is  placed  on  the  glands  of  the 
disc,  on  one  side  of  a leaf,  as  near  as  possible  to 
its  circumference,  the  tentacles  on  this  side  are  first 
affected,  those  on  the  opposite  side  much  later,  or,  as 
often  occurred,  not  at  all.  /This  was  repeatedly  proved 
by  trials  with  bits  of  meat ; but  I will  here  give  only 
the  case  of  a minute  fly,  naturally  caught  and  still 
alive,  which  I found  adhering  by  its  delicate  feet  to 
the  glands  on  the  extreme  left  side  of  the  central  disc. 
The  marginal  tentacles  on  this  side  closed  inwards 
and /killed  the  fly,  and  after  a time  the  edge  of  the 
leaf  on  this  side  also  became  inflected,  and  thus 
remained  for  several  days,  whilst  neither  the  tentacles 
nor  the  edge  on  the  c*pposite  side  were  in  the  least 
affected. 

If  young  and  acti^  3 leaves  are  selected,  inorganic 
particles  not  larger  than  the  head  of  a small  pin, 
placed  on  the  central  glands,  sometimes  cause  the 


22  DROSERA  ROTUNDIFOLIA.  Chap.  Ill 

outer  tentacles  to  bend  inwards.  But  tliis  follows| 
much  more  surely  and  quickly,  if  the  object  containsj' 
nitrogenous  matter  which  can  be  dissolved  by  thei 
secretion.  On  one  occasion  I observed  the  follow- 
ing unusual  circumstance.  Small  bits  of  raw  meat 
(which  acts  more  energetically  than  any  other  sul>! 
stance),  of  paper,  dried  moss,  and  of  the  quill  of 
pen  were  placed  on  several  leaves,  and  they  were  all 
embraced  equally  well  in  about  2 hrs.  On  othe:^ 
occasions  the  above-named  substances,  or  more  com- 
monly particles  of  glass,  coal-cinder  (taken  from  the 
fire),  stone,  gold-leaf,  dried  grass,  cork,  blotting-paper, 
cotton- woo],  and  hair  rolled  up  into  little  balls,  were 
used,  and  these  substances,  though  they  were  some- 
times well  embraced,  often  caused  no  movement  what- 
ever in  the  outer  tentacles,  or  an  extremely  slight  and 
slow  movement.  Yet  these  same  leaves  were  proved  to 
be  in  an  active  condition,  as  they  were  excited  to  move 
by  substances  yielding  soluble  nitrogenous  matter, 
such  as  bits  of  raw  or  roast  meat,  the  yolk  or  white  of 
boiled  eggs,  fragments  of  insects  of  all  orders,  spiders, 
&c.  I will  give  only  two  instances.  Minute  flies  w ere 
placed  on  the  discs  of  several  leaves,  and  on  others 
balls  of  paper,  bits  of  moss  and  quill  of  about  the  same 
size  as  the  flies,  and  the  latter  w^ere  well  embraced 
in  a few  hours  ; whereas  after  25  hrs.  only  a very 
few  tentacles  were  inflected  over  the  other  objects. 
The  bits  of  paper,  moss,  and  quill  w^ere  then  removed 
from  these  leaves,  and  bits  of  raw  meat  placed  on  them ; 
and  now  all  the  tentacles  were  soon  energetically 
inflected. 

Again,  particles  of  coal-cinder  (w^eighing  rather  more 
than  the  flies  used  in  the  last  experiment)  were  placed 
on  the  centres  of  three  leaves : after  an  interval  of 
19  hrs.  one  of  the  particles  was  tolerably  well  embraced ; 


(iiiAP.  n.  INFLECTION'  INDIRECTLY  CAUSED.  23 

second  by  a very  few  tentacles ; and  a third  by  none. 
j[  then  removed  the  particles  from  the  two  latter  leaves, 
dnd  put  on  them  recently  killed  flies.  These  were 
f^jairly  well  embraced  in  hrs.  and  thoroughly  after 
hrs. ; the  tentacles  remaining  inflected  for  many 
sjubsequent  days.  On  the  other  hand,  the  one  leaf 
which  had  in  the  course  of  19  hrs.  embraced  the  bit  of 
dinder  moderately  well,  and  to  which  no  fly  was  given, 
after  an  additional  33  hrs.  (i.  e.  in  52  hrs.  from  the 
time  when  the  cinder  was  put  on)  was  completely 
re-expanded  and  ready  to  act  again. 

From  these  and  numerous  other  experiments  not 
worth  giving,  it  is  certain  that  inorganic  substances, 
or  such  organic  substances  as  are  not  attacked  by  the 
secretion,  act  much  less  quickly  and  efficiently  than 
organic  substances  yielding  soluble  matter  which  is 
absorbed.  Moreover,  I have  met  with  very  few  excep- 
tions to  the  rule,  and  these  exceptions  apparently 
depended  on  the  leaf  having  been  too  recently  in 
action,  that  the  tentacles  remain  clasped  for  a much 
longer  time  over  organic  bodies  of  the  nature  just 
specified  than  over  those  which  are  not  acted  on  by 
the  secretion,  or  over  inorganic  objects.* 


* Owing  to  the  extraordinary- 
belief  held  by  M.  Ziegler  (‘  Coinp- 
tes  rendus/  May  1872,  p.  122), 
that  albuminous  substances,  if 
held  for  a moment  between  the 
fingers,  acquire  the  property  of 
making  the  tentacles  of  Drosera 
contract,  whereas,  if  not  thus  held, 
they  have  no  such  power,  I tried 
some  experiments  with  great  care, 
but  the  results  did  not  confirm 
this  belief.  Red-hot  cinders  were 
j taken  out  of  the  fire,  and  bits 
I of  glass,  cotton-thread,  blotting 
; paper  and  thin  slices  of  cork 
I were  immersed  in  boiling  water ; 


and  particles  were  then  placed 
(every  instrument  with  which 
they  were  touched  having  been 
previously  immersed  in  boiling 
water)  on  the  glands  of  several 
leaves,  and  they  acted  in  exactly 
the  same  manner  as  other  par- 
ticles, which  had  been  purposely 
handled  for  some  time.  Bits  of 
a boiled  egg,  cut  with  a knife 
which  had  been  washed  in  boiling 
water,  also  acted  like  any  other 
animal  substance.  I breathed  on 
some  leaves  for  above  a minute, 
and  repeated  the  act  two  or  three 
times,  with  my  mouth  close  to 


24 


DROSERA  ROTUNDIFOLIA. 


I 

Chap.  !](. 


The  Inflection  of  the  Exterior  Tentacles  as  directly  caused, 
hy  Objects  left  in  Contact  with  their  Glands,  j 

I made  a vast  number  of  trials  by  placing,  by  means 
of  a fine  needle  moistened  with  distilled  water,  and 
with  the  aid  of  a lens,  particles  of  various  substances 
on  the  viscid  secretion  surrounding  the  glands  of  tho 
outer  tentacles.  I experimented  on  both  the  oval  and 
long-headed  glands.  When  a particle  is  thus  placed 
on  a single  gland,  the  movement  of  the  tentacle  is 
particularly  well  seen  in  contrast  with  the  stationary 
condition  of  the  surrounding  tentacles.  (See  previous 
fig.  6.)  In  four  cases  small  particles  of  raw  meat 
caused  the  tentacles  to  be  greatly  inflected  in  between 
5 and  6 m.  Another  tentacle  similarly  treated, 
and  observed  with  special  care,  distinctly,  though 
slightly,  changed  its  position  in  10  s.  (seconds) ; and 
this  is  the  quickest  movement  seen  by  me.  In  2 m. 
30  s.  it  had  moved  through  an  angle  of  about  45^^. 
The  movement  as  seen  through  a lens  resembled  that 
of  the  hand  of  a large  clock.  In  5 m.  it  had  moved 
through  90^,  and  when  I looked  again  after  10  m., 
the  particle  had  reached  the  centre  of  the  leaf;  so 
that  the  whole  movement  was  completed  in  less 


them,  but  this  produced  no  etfect. 
I may  here  add,  as  showing  that 
the  leaves  are  not  acted  on  by  the 
odour  of  nitrogenous  substances, 
that  pieces  of  raw  meat  stuck  on 
needles  were  fixed  as  close  as 
possible,  without  actual  contact, 
to  several  leaves,  but  produced 
no  efiect  whatever.  On  the  other 
hand,  as  we  shall  hereafter  see, 
the  vapours  of  certaiu  volatile 
substances  and  fluids,  such  as  of 
carbonate  of  ammonia,  chloro- 
form, certaiu  essential  oib,  &c., 


cause  inflection.  M.  Ziegler 
makes  still  more  extraordinary 
statements  with  respect  to  the 
power  of  animal  substances,  which 
have  been  left  close  to,  but  not  in 
contact  with,  sulphate  of  quinine, 
fl’he  action  of  salts  of  quinine  will 
be  described  in  a future  chapter. 
Since  the  appearance  of  the  paper 
above  referred  to,  M.  Ziegler  has 
published  a book  on  the  same 
subject,  entitled,  ‘ Atonicite  et 
Zoicitc,’  1874. 


IL  iNFLECTION  INDIRECTLY  CAUSED.  25 

t hail  17  in.  30  s.  In  the  course  of  some  hours  this 
uiiintite  bit  of  meat,  from  having  been  brought  into 
ciont^ct  with  some  of  the  glands  of  the  central  disc, 
ahted  centrifugally  on  the  outer  tentacles,  which  all  be- 
came closely  inflected.  Fragments  of  flies  were  placed 
op.  the  glands  of  four  of  the  outer  tentacles,  ex- 
tfended  in  the  same  plane  with  that  of  the  blade,  and 
three  of  these  fragments  were  carried  in  35  m.  through 
a*^  angle  of  180°  to  the  centre.  The  fragment  on 
the  fourth  tentacle  was  very  minute,  and  it  was 
not  carried  to  the  centre  until  3 hrs.  had  elapsed.  In 
three  other  cases  minute  flies  or  portions  of  larger 
ones  were  carried  to  the  centre  in  1 hjr.  30  s.  In 
these  seven  cases,  the  fragments  or  small  flies,  which 
had  been  carried  by  a single  tentacle  to  the  central 
glands,  were  well  embraced  by  the  other  tentacles 
after  an  interval  of  from  4 to  10  hrs. 

I also  placed  in  the  manner  just  described  six  small 
balls  of  writing-paper  (rolled  up  by  the  aid  of  pincers, 
so.  that  they  were  not  touched  by  my  fingers)  on  the 
glands  of  six  exterior  tentacles  on  distinct  leaves; 
three  of  these  were  carried  to  the  centre  in  about  1 hr., 
and  the  other  three  in  rather  more  than  4 hrs. ; but 
after  24  hrs.  only  two  of  the  six  balls  were  well  em- 
braced by  the  other  tentacles.  It  is  possible  that 
the  secretion  may  have  dissolved  a trace  of  glue  or 
animalised  matter  from  the  balls  of  paper.  Four  par- 
ticles of  coal-cinder  were  then  placed  on  the  glands 
of  four  exterior  tentacles;  one  of  these  reached 
the  centre  in  3 hrs.  40  m. ; the  second  in  9 hrs. ; the 
third  within  24  hrs.,  but  had  moved  only  part  of  the 
way  in  9 hrs. ; whilst  the  fourth  moved  only  a very 
short  distance  in  24  hrs.,  and  never  moved  any  farther. 
Of  the  above  three  bits  of  cinder  which  were  ultimately 
carried  to  the  centre,  one  alone  was  well  embraced  by 


26 


DROSERA  ROTUNDIFOLTA. 


Chap.  lij, 

I 

many  of  the  other  tentacles.  We  here  see  clearly  that 
such  bodies  as  particles  of  cinder  or  little  balls  o£ 
paper,  after  being  carried  by  the  tentacles  to  th^^ 
central  glands,  act  very  differently  from  fragments  of 
flies,  in  causing  the  movement  of  the  surrounding 
tentacles.  I 

I made,  without  carefully  recording  the  times  of 
movement,  many  similar  trials  with  other  substances, 
such  as  splinters  of  white  and  blue  glass,  particles  of 
cork,  minute  bits  of  gold-leaf,  &c. ; and  the  propor- 
tional number  of  cases  varied  much  in  which  the 
tentacles  reached  the  centre,  or  moved  only  slightly, 
or  not  at  all.  One  evening,  particles  of  glass  and 
cork,  rather  larger  than  those  usually  employed,  w^ere 
placed  on  about  a dozen  glands,  and  next  morning, 
after  13  hrs.,  every  single  tentacle  had  carried  its  little 
load  to  the  centre ; but  the  unusually  large  size  of  the 
particles  will  account  for  this  result.  In  another  case 
of  the  particles  of  cinder,  glass,  and  thread,  placed 
on  separate  glands,  were  carried  towards,  or  actually 
to,  the  centre ; in  another  case  -J,  in  another  -yV? 
in  the  last  case  only  were  thus  carried  inwards,  the 
small  proportion  being  here  due,  at  least  in  part,  to  the 
leaves  being  rather  old  and  inactive.  Occasionally  a 
gland,  with  its  light  load,  could  be  seen  through  a 
strong  lens  to  move  an  extremely  short  distance  and 
then  stop ; this  was  especially  apt  to  occur  when  ex- 
cessively minute  particles,  much  less  than  those  of 
which  the  measurements  will  be  immediately  given, 
were  placed  on  glands ; so  that  we  here  have  nearly 
the  limit  of  any  actio  . 

/ I was  so  much  snr  aised  at  the  smallness  of  the  par- 
ticles which  caused  the  tentacles  to  become  greatly 
inflected  that  it  SL'emed  worth  while  carefully  to 
ascertain  how  minute  a particle  would  plainly  actf^ 


C^HAP.n.  INFLECTION  INDIRECTLY  CAUSED.  27 

Accordingly  measured  lengths  of  a narrow  strip  of 
Wotting  paper,  of  fine  cotton-thread,  and  of  a woman’s 
Ijiair,  were  carefully  weighed  for  me  by  Mr.  Trenham 
Jleeks,  in  an  excellent  balance,  in  the  laboratory  in 
Jiermyn  Street.  Short  bits  of  the  paper,  thread,  and 
hair  were  then  cut  off  and  measured  by  a micrometer, 
so  that  their  weights  could  be  easily  calculated.  The 
bits  were  placed  on  the  viscid  secretion  surrounding  the 
glands  of  the  exterior  tentacles,  with  the  precautions 
(ilready  stated,  and  I am  certain  that  the  gland  itself 
was  never  touched ; nor  indeed  would  a single  touch 
have  produced  any  effect.  A bit  of  the  blotting-paper, 
weighing  of  a grain,  was  placed  so  as  to  rest  on 
three  glands  together,  and  all  three  tentacles  slowly 
curved  inwards;  each  gland,  therefore,  supposing  the 
weight  to  be  distributed  equally,  could  have  been 
pressed  on  by  only  — jVt  ^ grain,  or  *0464  of  a milli- 
gramme. Five  nearly  equal  bits  of  cotton-thread  were 
tried,  and  all  acted.  The  shortest  of  these  was  ^ of 
an  inch  in  length,  and  weighed  of  a grain.  The 
tentacle  in  this  case  was  considerably  inflected  in 
1 hr.  30  m.,  and  the  bit  of  thread  was  carried  to  the 
centre  of  the  leaf  in  1 hr.  40  m.  Again,  two  particles 
of  the  thinner  end  of  a woman’s  hair,  one  of  these 
being  of  an  inch  in  length,  and  weighing  -g-rl  tt  of 
a grain,  the  other  — ^-o  of  an  inch  in  length,  and  weigh- 
ing of  course  a little  more,  were  placed  on  two  glands  on 
opposite  sides  of  the  same  leaf,  and  these  two  tentacles 
were  inflected  halfway  towards  the  centre  in  1 hr.  10m.; 
all  the  many  other  tentacles  round  the  same  leaf  re- 
maining motionless.  The  appearance  of  this  one  leaf 
showed  in  an  unequivocal  manner  that  these  minute 
particles  sufficed  to  cause  the  tentacles  to  bend.  Alto- 
gether, ten  such  particles  of  hair  Avere  placed  on  ten 
glands  on  several  leaves,  and  seven  of  them  caused 


28 


DROSERA.  ROTUNDIFOLIA. 


Chap.  IIl^ 


the  tentacles  to  move  in  a conspicuous  manner.  The 
smallest  particle  which  was  tried,  and  which  acted/ 
plainly,  was  only  -x-oVo  (*203  millimetre)  in. 

length,  and  weighed  the  y-g- tr^  ^ grain,  or  *00082^ 
milligramme.  In  these  several  cases,  not  only  was  the 
inflection  of  the  tentacles  conspicuous,  but  the  purple 
fluid  within  their  cells  became  aggregated  into  little 
masses  of  protoplasm,  in  the  manner  to  be  described  in 
the  next  chapter ; and  the  aggregation  was  so  plain 
that  I could,  by  this  clue  alone,  have  readily  picked 
out  under  the  microscope  all  the  tentacles  which  had 
carried  their  light  loads  towards  the  centre,  from  the 
hundreds  of  other  tentacles  on  the  same  leaves  which 
had  not  thus  acted. 

My  surprise  was  greatly  excited,  not  only  by  the 
minuteness  of  the  particles  which  caused  movement, 
but  how  they  could  possibly  act  on  the  glands  ; for  it 
must  be  remembered  that  they  were  laid  with  the 
greatest  care  on  the  convex  surface  of  the  secretion. 
At  first  I thought — but,  as  I now  know,  erroneously — 
that  particles  of  such  low  specific  gravity  as  those  of 
cork,  thread,  and  paper,  would  never  come  into  contact 
with  the  surfaces  of  the  glands.  The  particles  cannot 
act  simply  by  their  weight  being  added  to  that  of  the 
secretion,  for  small  drops  of  water,  many  times  heavier 
than  the  particles,  were  repeatedly  added,  and  never 
produced  any  efi’ect.  Nor  does  the  disturbance  of  the 
secretion  produce  any  effect,  for  long  threads  were 
drawn  out  by  a needle,  and  affixed  to  some  adjoining 
object,  and  thus  left  for  hours ; but  the  tentacles 
remained  motionless. 


' I also  carefully  removed  the  secretion  from  four 
glands  with  a sharply  pointed  piece  of  blotting-paper, 
so  that  they  were  exposed  for  a time  naked  to  the  air, 
but  this  caused  no  movement ; yet  these  glands  were 


INFLECTION  INDIRECTLY  CAUSED. 


29 


C^AP.  11. 

(A  an  efficient  state,  for  after  24  hrs.  had  elapsed,  they 
were  tried  with  bits  of  meat,  and  all  became  quickly 
inflected.  ^ It  then  occurred  to  me  that  particles  float- 
ing on  the  secretion  would  cast  shadows  on  the  glands, 
which  might  be  sensitive  to  the  interception  of  the 
light.  Although  this  seemed  highly  improbable,  as 
minute  and  thin  splinters  of  colourless  glass  acted 
powerfully,  nevertheless,  after  it  was  dark,  I put  on, 
by  the  aid  of  a single  tallow  candle,  as  quickly  as 
possible,  particles  of  cork  and  glass  on  the  glands  of  a 
dozen  tentacles,  as  well  as  some  of  meat  on  other 
glands,  and  covered  them  up  so  that  not  a ray  of  light 
could  enter ; but  by  the  next  morning,  after  an  interval 
of  13  hrs.,  all  the  particles  were  carried  to  the  centres 
of  the  leaves. 

These  negative  results  led  me  to  try  many  more 
experiments,  by  placing  particles  on  the  surface  of  the 
drops  of  secretion,  observing,  as  carefully  as  I could, 
whether  they  penetrated  it  and  touched  the  surface  of 
the  glands.  The  secretion,  from  its  weight,  generally 
forms  a thicker  layer  on  the  under  than  on  the  upper 
sides  of  the  glands,  whatever  may  be  the  position  of 
the  tentacles.  Minute  bits  of  dry  cork,  thread,  blotting 
paper,  and  coal  cinders  were  tried,  such  as  those  pre- 
viously employed;  and  I now  observed  that  they 
absorbed  much  more  of  the  secretion,  in  the  course  of 
a few  minutes,  than  I should  have  thought  possible and 
as  they  had  been  laid  on  the  upper  surface  of  the  secre- 
tion, where  it  is  thinnest,  they  were  often  drawn  down, 
after  a time,  into  contact  with  at  least  some  one  point 
of  the  gland.  With  respect  to  the  minute  splinters 
of  glass  and  particles  of  hair,  I observed  that  the 
secretion  slowly  spread  itself  a little  over  their  sur- 
faces, by  which  means  they  were  likewise  drawn  down- 
wards or  sideways,  and  thus  one  end,  or  some  minute 


30  DROSERA  ROTUNDIFOLIA.  Chap.  IJ. 

prominence,  often  came  to  touch,  sooner  or  later,  the 
gland. 

In  the  foregoing  and  following  cases,  it  is  probable 
that  the  vibrations,  to  which  the  furniture  in  every 
room  is  continually  liable,  aids  in  bringing  the  par- 
ticles into  contact  with  the  glands.  But  as  it  was 
sometimes  difficult,  owing  to  the  refraction  of  the  secre- 
tion, to  feel  sure  whether  the  particles  were  in  contacjt, 
I tried  the  following  experiment.  Unusually  minute 
particles  of  glass,  hair,  and  cork,  were  gently  placed  on 
the  drops  round  several  glands,  and  very  few  of  the 
tentacles  moved.  Those  which  were  not  affected  were 
left  for  about  half  an  hour,  and  the  particles  were 
then  disturbed  or  tilted  up  several  times  with  a fine 
needle  under  the  microscope,  the  glands  not  being 
touched.  And  now  in  the  course  of  a few  minutes 
almost  all  the  hitherto  motionless  tentacles  began  to 
move ; and  this,  no  doubt,  was  caused  by  one  end  or 
some  prominence  of  the  particles  having  come  into 
contact  with  the  surface  of  the  glands.  But  as  the 
particles  were  unusually  minute,  the  movement  was 
small. 

Lastly,  some  dark  blue  glass  pounded  into  fine 
splinters  was  used,  in  order  that  the  points  of  the  par- 
ticles might  be  better  distinguished  when  immersed  in 
the  secretion ; and  thirteen  such  particles  were  placed 
in  contact  with  the  depending  and  therefore  thicker 
part  of  the  drops  round  so  many  glands.  Five  of  the 
tentacles  began  moving  after  an  interval  of  a few 
minutes,  and  in  these  cases  I clearly  saw  that  the  par- 
ticles touched  the  lower  surface  of  the  gland.  A sixth 
tentacle  moved  after  1 hr.  45  m.,  and  the  particle 
was  now  in  contact  with  the  gland,  which  was  not  the 
case  at  first.  So  it  was  with  the  seventh  tentacle,  but 
its  movement  did  not  begin  until  3 hrs.  45  m.  had 


lAP.  II. 


IKFLECTION  INDIEECTLY  CAUSED. 


31 


elapsed.  ^The  remaining  six  tentacles  never  moved 
as  long  as  they  were  observed ; )^nd  the  particles 
apparently  never  came  into  contact  with  the  surfaces 
of  the  glands.  / 

From  these  experiments  we  learn  that  particles  not 
containing  soluble  matter,  when  placed  on  glands,  often 
cause  the  tentacles  to  begin  bending  in  the  course  of 
from  one  to  five  minutes  ; and  that  in  such  cases  the 
particles  have  been  from  the  first  in  contact  with  the 
surfaces  of  the  glands.  When  the  tentacles  do  not 
begin  moving  for  a much  longer  time,  namely,  from 
half  an  hour  to  three  or  four  hours,  the  particles 
have^  been  slowly  brought  into  contact  with  the 
glands,  either  by  the  secretion  being  absorbed  by  the 
particles  or  by  its  gradual  spreading  over  them,  to- 
gether with  its  consequent  quicker  evaporation. 
When  the  tentacles  do  not  move  at  all,  the  particles 
have  never  come  into  contact  with  the  glands,  or  in 
some  cases  the  tentacles  may  not  have  been  in  an 
active  condition.  In  order  to  excite  movement,  it  is 
indispensable  that  the  particles  should  actually  rest  on 
the  glands ; for  a touch  .once,  twice,  or  even  thrice 
repeated  by  any  hard  body  is  not  sufficient  to  excite 
movement.  / 

Another  experiment,  showing  that  extremely  mi- 
nute particles  act  on  the  glands  when  immersed  in 
water,  may  here  be  given.  A grain  of  sulphate  of 
quinine  was  added  to  an  ounce  of  water,  which  was 
not  afterwards  filtered ; an  1 on  placing  three  leaves  in 
ninety  minims  of  this  flui(  , I was  much  surprised  to  find 
that  all  three  leaves  wei  j greatly  inflected  in  15  m. ; 
for  I knew  from  previous  trials  that  the  solution  does 
not  act  so  quickly  as  this.  It  immediately  occurred 
to  me  that  the  particles  of  the  undissolved  salt,  which 
were  so  light  as  to  float  about,  might  have  come 


32  DBOSEKA  KOTUNDIFOIilA.  Chap.;  ' 

0 

into  contact  with  the  glands,  and  caused  this  rapid 
movement.  Accordingly  I added  to  some  distilled 
water  a pinch  of  a quite  innocent  substance,  namely, 
precipitated  carbonate  of  lime,  which  consists  of  an 
impalpable  powder ; I shook  the  mixtui-e,  and  thus  got 
a fluid  like  thin  milk.  Two  leaves  were  immersed  in 
it,  and  in  6 m.  almost  every  tentacle  was  much 
inflected.  I placed  one  of  these  leaves  under  the 
microscope,  and  saw  innumerable  atoms  of  lime  ad- 
hering to  the  external  surface  of  the  secretion.  Some, 
however,  had  penetrated  it,  and  were  lying  on  the  sur- 
faces of  the  glands ; and  no  doubt  it  was  these  particles 
which  caused  the  tentacles  to  bend.  When  a leaf  is  im- 
mersed in  water,  the  secretion  instantly  swells  much ; 
and  I presume  that  it  is  ruptured  here  and  there,  so 
that  little  eddies  of  water  rush  in.  If  so,  we  can  under- 
stand how  the  atoms  of  chalk,  which  rested  on  the 
surfaces  of  the  glands,  had  penetrated  the  secretion. 
Anyone  who  has  rubbed  precipitated  chalk  between, 
his  fingers  will  have  perceived  how  excessively  fine 
the  powder  is.  No  doubt  there  must  be  a limit,  bey  ond 
which  a particle  would  be  too  small  to  act  on  a gland';- 
but  what  this  limit  is,  I know  not.  I have  often  seen 
fibres  and  dust,  which  had  fallen  from  the  air,  on  the 
glands  of  plants  kept  in  my  room,  and  these  never 
induced  any  movement ; but  then  such  particles  lay 
on  the  surface  of  the  secretion  and  never  reached  the 
gland  itself. 

Finally,  it  is  an  extraordinary  fact  that  a little 
bit  of  soft  thread,  of  an  inch  in  length  and  Aveigh- 
ing  -aV oT  ^ grain,  or  of  a human  hair, 

inch  ill  length  and  weighing  only  -7-3 1 tit  ^ grain 
(•000822  milligramme),  or  particles  of  precipitated 
chalk,  after  resting  for  a short  time  on  a gland, 
should  induce  some  change  in  its  cells,  exciting  them 


Ohap.  II. 


INFLECTION  DIRECTLY  CAUSED. 


33 


to  transmit  a motor  impulse  throughout  the  whole 
length  of  the  pedicel,  consisting  of  about  twenty  cells, 
to  near  its  base,  causing  this  part  to  bend,  and  the 
tentacle  to  sweep  through  an  angle  of  above  180°. 
That  the  contents  of  the  cells  of  the  glands,  and  after- 
wards those  of  the  pedicels,  are  affected  in  a plainly 
visible  manner  by  the  pressure  of  minute  particles,  we 
shall  have  abundant  evidence  when  we  treat  of  the 
aggregation  of  protoplasm.  But  the  case  is  much  more 
remarkable  than  as  yet  stated ; for  the  particles  are  sup- 
ported by  the  viscid  and  dense  secretion ; nevertheless, 
even  smaller  ones  than  those  of  which  the  measure- 
ments have  been  given,  when  brought  by  an  insensibly 
slow  movement,  through  the  means  above  specified,  into 
contact  with  the  surface  of  a gland,  act  on  it,  and  the 
tentacle  bends.  The  pressure  exerted  by  the  particle 
of  hair,  weighing  only  ^ grain  and  supported 

by  a dense  fluid,  must  have  been  inconceivably  slight. 
We  may  conjecture  that  it  could  hardly  have  equalled 
the  millionth  of  a grain;  and  we  shall  hereafter  see 
that  far  less  than  the  millionth  of  a grain  of  phos- 
phate of  ammonia  in  solution,  when  absorbed  by  a 
gland,  acts  on  it  and  induces  movement.  A bit  of 
hair,  ^ of  an  inch  in  length,  and  therefore  much 
larger  than  those  used  in  the  above  experiments,  was 
not  perceived  when  placed  on  my  tongue  ;l  and  it  is 
extremely  doubtful  whether  any  nerve  in  the  human 
body,  even  if  in  an  inflamed  condition,  would  be  in 
any  way  affected  by  such  a particle  supported  in  a 
dense  fluid,  and  slowly  brought  into  contact  with  the 
nerve.  Yet  the  cells  of  the  glands  of  Drosera  are  thus 
excited  to  transmit  a motor  impulse  to  a distant  point, 
inducing  movement.  It  appears  to  me  that  hardly 
any  more  remarkable  fact  than  this  has  been  observed 
in  the  vegetable  kingdom,  j 


34 


DROSERA  ROTUNDIFOLIA. 


Chap.  II 


The  Inflection  of  the  Exterior  Tentacles,  when  their  Glands 
are  excited  hy  Repeated  Touches. 

^ We  have  already  seen  that,  if  the  central  glands 
are  excited  by  being  gently  brushed,  they  trans- 
mit a motor  impulse  to  the  exterior  tentacles, 
pausing  them  to  bend;  and  we  have  now  to  con- 
sider the  effects  which  follow  from  the  glands  of 
the  exterior  tentacles  being  themselves  touched.  On 
several  occasions,  a large  number  of  glands  were 
touched  only  once  with  a needle  or  fine  brush, 
hard  enough  to  bend  the  whole  flexible  tentacle; 
and  though  this  must  have  caused  a thousand- 
fold greater  pressure  than  the  weight  of  the  above 
described  particles,  not  a tentacle  moved.  On 
another  occasion  forty-five  glands  on  eleven  leaves 
were  touched  once,  twice,  or  even  thrice,  with  a 
needle  or  stiff  bristle.  This  was  done  as  quickly  as 
possible,  but  with  force  sufBcient  to  bend  the  ten- 
tacles ; yet  only  six  of  them  became  inflected, — three 
plainly,  and  three  in  a slight  degree.  In  order  to 
ascertain  whether  these  tentacles  which  were  not 
affected  were  in  an  efficient  state,  bits  of  meat  were 
placed  on  ten  of  them,  and  they  all  soon  became  greatly 
incurved.  On  the  other  hand,  when  a large  number  of 
glands  were  struck  four,  five,  or  six  times  with  the 
same  force  as  before,  a needle  or  sharp  splinter  of 
glass  being  used,  a much  larger  proportion  of  tentacles 
became  inflected;  but  the  result  was  so  uncertain 
as  to-  seem  capricious.  For  instance,  I struck  in 
the  above  manner  three  glands,  which  happened  to 
be  extremely  sensitive,  and  all  three  were  inflected 
almost  as  quickly  as  if  bits  of  meat  had  been  placed 
on  them.  On  another  occasion  I gave  a single  for- 


Chap.  II.  THE  EFFECTS  OF  KEPEATED  TOUCHES, 


35 


cible  touch  to  a considerable  number  of  glands,  and 
not  one  moved  ; but  these  same  glands,  after  an  inter- 
val of  some  hours,  being  touched  four  or  five  times 
with  a needle,  several  of  the  tentacles  soon  became 
inflected. 

The  fact  of  a single  touch  or  even  of  two  or  three/ 
touches  not  causing  inflection  must  be  of  some  service 
to  the  plant ; as  during  stormy  weather,  the  glands 
cannot  fail  to  be  -occasionally  touched  by  the  tall 
blades  of  grass,  or  by  other  plants  growing  near ; and 
it  would  be  a great  evil  if  the  tentacles  were  thus 
brought  into  action,  for  the  act  of  re-expansion  takes 
a considerable  time,  and  until  the  tentacles  are  re- 
expanded they  cannot  catch  prey.  On  the  other 
hand,  extreme  sensitiveness  to  slight  pressure  is  of  the 
highest  service  to  the  plant ; for,  as  we  have  seen,  if 
the  delicate  feet  of  a minute  struggling  insect  press 
ever  so  lightly  on  the  surfaces  of  two  or  three  glands, 
the  tentacles  bearing  these  glands  soon  curl  inwards 
and  carry  the  insect  with  them  to  the  centre,  causing, 
after  a time,  all  the  circumferential  tentacles  to 
embrace  it.  Nevertheless,  the  movements  of  the 
plant  are  not  perfectly  adapted  to  its  requirements; 
for  if  a bit  of  dry  moss,  peat,  or  other  rubbish,  is 
blown  on  to  the  disc,  as  often  happens,  the  tentacles 
clasp  it  in  a useless  manner.  They  soon,  however, 
discover  their  mistake  and  release  such  innutritiou^ 
objects. 

It  is  also  a remarkable  fact,  that  drops  of  water  fall- 
ing from  a height,  whether  under  the  form  of  natural 
or  artificial  rain,  do  not  cause  the  tentacles  to  move ; 
yet  the  drops  must  strike  the  glands  with  considerable 
force,  more  especially  after  the  secretion  has  been  all 
washed  away  by  heavy  rain  ; and  this  often  occurs. 


36 


DROSERA  ROTUNDIFOLIA. 


Chap.  II. 


though  the  secretion  is  so  viscid  that  it  can  be  re- 
moved with  difficulty  merely  by  waving  the  leaves  in 
water.  If  the  falling  drops  of  water  are  small,  they 
adhere  to  the  secretion,  the  weight  of  which  must  be 
increased  in  a much  greater  degree,  as  before  re- 
marked, than  by  the  addition  of  minute  particles  of 
solid  matter ; yet  the  drops  never  cause  the  tentacles 
to  become  inflected.  It  would  obviously  have  been  a 
great  evil  to  the  plant  (as  in  the  case  of  occasional 
touches)  if  the  tentacles  were  excited  to  bend  by 
/ every  shower  of  rain ; but  this  evil  has  been  avoided 
by  the  glands  either  having  become  through  habit 
insensible  to  the  blows  and  prolonged  pressure  of 
drops  of  water,  or  to  their  having  been  originally 
rendered  sensitive  solely  to  the  contact  of  solid  bodies. 

^We  shall  hereafter  see  that  the  filaments  on  the  leaves 
of  Dionaea  are  likewise  insensible  to  the  impact  of 
fluids,  though  exquisitely  sensitive  to  momentary 
touches  from  any  solid  body. 

When  the  pedicel  of  a tentacle  is  cut  off  by  a 
sharp  pair  of  scissors  quite  close  beneath  the  gland, 
the  tentacle  generally  becomes  inflected.  I tried  this 
experiment  repeatedly,  as  I was  much  surprised  at  the 
fact,  for  all  other  parts  of  the  pedicels  are  insensible  to 
any  stimulus.  These  headless  tentacles  after  a time 
re-expand ; but  I shall  return  to  this  subject.  On  the 
other  hand,  I occasionally  succeeded  in  crushing  a 
gland  between  a pair  of  pincers,  but  this  caused  no 
inflection.  In  this  latter  case  the  tentacles  seem 
paralysed,  as  likewise  follows  from  the  action  of  too 
strong  solutions  of  certain  salts,  and  by  too  great 
heat,  whilst  weaker  solutions  of  the  same  salts  and  a 
more  gentle  heat  cause  movement.  We  shall  also  see 
in  future  chapters  that  various  other  fluids,  some 


Chap.  11. 


DROPS  OF  WATER. 


37 


vapours,  and  oxygen  (after  the  plant  has  been  for  some 
time  excluded  from  its  action),  all  induce  inflection, 
and  this  likewise  results  from  an  induced  galvanic 
current.* 


* My  son  Francis,  guided  by 
the  observations  of  Dr.  Burdon 
Sanderson  on  Dionaea,  finds  that 
if  two  needles  are  inserted  into 
the  blade  of  a leaf  of  Drosera,  the 
tentacles  do  not  move ; but  that  if 
similar  needles  in  connection  with 


the  secondary  coil  of  a Du  Bois 
inductive  apparatus  are  inserted, 
the  tentacles  curve  inwards  in  the 
course  of  a few  minutes.  My  son 
hopes  soon  to  publish  an  account 
of  his  observations. 


38 


DROSERA  ROTUNDIFOLIA. 


Chap.  JII. 


CHAPTEE  III. 

Aggregation  op  the  Protoplasm  within  the  Cells  of  the 
Tentacles. 

Nature  of  the  contents  of  the  cells  before  aggregation  — Various 
causes  which  excite  aggregation — The  process  commences  within 
the  glands  and  travels  down  the  tentacles  — Description  of  the 
aggregated  masses  and  of  their  spontaneous  movements — Currents 
of  protoplasm  along  the  walls  of  the  cells — Action  of  carbonate 
of  ammonia — The  granules  in  the  protoplasm  which  flows  along 
the  walls  coalesce  with  the  central  masses — Minuteness  of  the 
quantity  of  carbonate  of  ammonia  causing  aggregation  — Action 
of  other  salts  of  ammonia  — Of  other  substances,  organic  fluids, 
&c. — Of  water — Of  heat — Redissolution  of  the  aggregated  masses 
— Proximate  causes  of  the  aggregation  of  the  protoplasm  — 
Summary  and  concluding  remarks — Supplementary  observations 
on  aggregation  in  the  roots  of  plants. 

I WILL  here  interrupt  my  account  of  the  movements 
of  the  leaves,  and  describe  the  phenomenon  of  aggre- 
gation, to  which  subject  I have  already  alluded.  If 
the  tentacles  of  a young,  yet  fully  matured  leaf,  that 
has  never  been  excited  or  become  inflected,  be  ex- 
amined, the  cells  forming  the  pedicels  are  seen  to  be 
filled  with  homogeneous,  purple  fluid.  The  walls  are 
lined  by  a layer  of  colourless,  circulating  protoplasm  ; 
but  this  can  be  seen  with  much  greater  distinctness 
after  the  process  of  aggregation  has  been  partly 
effected  than  before.  The  purple  fluid  which  exudes 
from  a crushed  tentacle  is  somewhat  coherent,  and 
does  not  mingle  with  the  surrounding  water;  it  con- 
tains much  flocculent  or  granular  matter.  But  this 
matter  may  have  been  generated  by  the  cells  having 
been  crushed ; some  degree  of  aggregation  having 
been  thus  almost  instantly  caused. 


Ohap.  III.  the  process  of  aggregation. 


39 


If  a tentacle  is  examined  some  hours  after  the  gland 
has  been  excited  by  repeated  touches,  or  by  an  in- 
organic or  organic  particle  placed  on  it,  or  by  the 
absorption  of  certain  fluids,  it  presents  a wholly 
changed  appearance.  The  cells,  instead  of  being  filled 
with  homogeneous  purple  fluid,  now  contain  variously 
shaped,  masses  of  purple  matter,  suspended  in  a colour- 
less or  almost  colourless  fluid.  The  change  is  so 
conspicuous  that  it  is  visible  through  a weak  lens, 
and  even  sometimes  by  the  naked  eye ; the  tentacles 
now  have  a mottled  appearance,  so  that  one  thus 
affected  can  be  picked  out  with  ease  from  all  the 
others.  The  same  result  follows  if  the  glands  on  the 
disc  are  irritated  in  any  manner,  so  that  the  exterior 
tentacles  become  inflected;  for  their  contents  will 
then  be  found  in  an  aggregated  condition,  although 
their  glands  have  not  as  yet  touched  any  object.  But 
aggregation  may  occur  independently  of  inflection, 
as  we  shall  presently  see.  By  whatever  cause  the 
process  may  have  been  excited,  it  commences  within 
the  glands,  and  then  travels  down  the  tentacles.  It 
can  be  observed  much  more  distinctly  in  the  upper 
cells  of  the  pedicels  than  within  the  glands,  as  these 
are  somewhat  opaque.  Shortly  after  the  tentacles  have 
re-expanded,  the  little  masses  of  protoplasm  are  all 
redissolved,  and  the  purple  fluid  within  the  cells  be- 
comes as  homogeneous  and  transparent  as  it  was  at 
first.  The  process  of  redissolution  travels  upwards 
from  the  bases  of  the  tentacles  to  the  glands,  and 
therefore  in  a reversed  direction  to  that  of  aggre- 
gation. Tentacles  in  an  aggregated  condition  were 
shown  to  Prof.  Huxley,  Dr.  Hooker,  and  Dr.  Burdon 
Sanderson,  who  observed  the  changes  under  the 
microscope,  and  were  much  struck  with  the  whole 
phenomenon. 


40 


DKOSERA  ROT  UNDIFOLIA. 


Chap.  HI. 


Tlie  little  masses  of  aggregated  matter  are  of  the 
most  diversified  shapes,  often  spherical  or  oval,  some- 
times much  elongated,  or  quite  irregular  with  thread- 
er necklace-like  or  club-formed  projections.  They 
consist  of  thick,  apparently  viscid  matter,  which  in 
the  exterior  tentacles  is  of  a purplish,  and  in  the 
short  discal  tentacles  of  a greenish,  colour.  These 
little  masses  incessantly  change  their  forms  and  posi- 
tions, being  never  at  rest.  A single  mass  will  often 
separate  into  two,  which  afterwards  reunite.  Their 
movements  are  rather  slow,  and  resemble  those  of 
Amoebae  or  of  the  white  corpuscles  of  the  blood.  We 


ABODE  FGH 


{Drosera  rotundifolia.) 

Diagram  of  the  same  cell  of  a tentacle,  showing  the  various  forms  successively 
assumed  by  the  aggregated  masses  of  protoplasm. 


may,  therefore,  conclude  that  they  consist  of  proto- 
plasm. If  their  shapes  are  sketched  at  intervals 
of  a few  minutes,  they  are  invariably  seen  to  have 
undergone  great  changes  of  form ; and  the  same 
cell  has  been  observed  for  several  hours.  Eight  rude, 
though  accurate  sketches  of  the  same  cell,  made  at 
intervals  of  between  2 m.  or  3 m.,  are  here  given 
(fig.  7),  and  illustrate  some  of  the  simpler  and  com- 
monest changes.  The  cell  A,  when  first  sketched, 
included  two  oval  masses  of  purple  protoplasm  touch- 
ing each  other.  These  became  separate,  as  shown 
at  B,  and  then  reunited,  as  at  C.  After  the  next 
interval  a very  common  appearance  was  presented — 


Chap.  III. 


THE  PROCESS  OF  AGGREGATION. 


41 


D,  namely,  the  formation  of  an  extremely  minute 
sphere  at  one  end  of  an  elongated  mass.  This  rapidly 
increased  in  size,  as  shown  in  E,  and  was  then  re- 
absorbed, as  at  F,  by  which  time  another  sphere  had 
been  formed  at  the  opposite  end. 

/ The  cell  above  figured  was  from  a tentacle  of  a dark 
red  leaf,  which  had  caught  a small  moth,  and  was 
examined  under  water.  As  I at  first  thought  that  the 
movements  of  the  masses  might  be  due  to  the  absorp- 
tion of  water,  I placed  a fly  on  a leaf,  and  when  after 
18  hrs.  all  the  tentacles  were  well  inflected,  these  were 
examined  without  being  immersed  in  water.  ^ The  cell 


1 2 3 4 5 6 7 8 


Fig.  8. 

(^Drosera  rotundifolia.') 

Diagram  of  the  same  cell  of  a tentacle,  showing  the  various  forms  successively 
assumed  by  the  aggregated  masses  of  protoplasm. 


here  represented  (fig.  8)  was  from  this  leaf,  being 
sketched  eight  times  in  the  course  of  15  m.  These 
sketches  exhibit  some  of  the  more  remarkable  changes 
which  the  protoplasm  undergoes.  At  first,  there  was 
at  the  base  of  the  cell  1,  a little  mass  on  a short 
footstalk,  and  a larger  mass  near  the  upper  end,  and 
these  seemed  quite  separate.  Nevertheless,  they  may 
have  been  connected  by  a fine  and  invisible  thread  of 
protoplasm,  for  on  two  other  occasions,  whilst  one 
mass  was  rapidly  increasing,  and  another  in  the  same 
cell  rapidly  decreasing,  I was  able  by  varying  the 
light  and  using  a high  power,  to  detect  a connecting 
thread  of  extreme  tenuity,  which  evidently  served  as 


42 


DKOSERA  ROTUNDIFOLTA. 


Chap.  III. 


the  channel  of  communication  between  the  two.  On 
the  other  hand,  such  connecting  threads  are  some- 
times seen  to  break,  and  their  extremities  then 
quickly  become  club-headed.  The  other  sketches  in 
fig.  8 show  the  forms  successively  assumed. 

Shortly  after  the  purple  fluid  within  the  cells  has 
become  aggregated,  the  little  masses  float  about  in  a 
colourless  or  almost  colourless  fluid ; and  the  layer 
of  white  granular  protoplasm  which  flows  along  the 
walls  can  now  be  seen  much  more  distinctly.  The 
stream  flows  at  an  irregular  rate,  up  one  wall  and 
down  the  opposite  one,  generally  at  a slower  rate 
across  the  narrow  ends  ©f  the  elongated  cells,  and  so 
round  and  round.  But  the  current  sometimes  ceases. 
The  movement  is  often  in  waves,  and  their  crests 
sometimes  stretch  almost  across  the  whole  width  of 
the  cell,  and  then  sink  down  again.  Small  spheres  of 
protoplasm,  apparently  quite  free,  are  often  driven  by 
the  current  round  the  cells ; and  filaments  attached 
to  the  central  masses  are  swayed  to  and  fro,  as  if 
struggling  to  escape.  Altogether,  one  of  these  cells 
with  the  ever  changing  central  masses,  and  with  the 
layer  of  protoplasm  flowing  round  the  walls,  presents 
a wonderful  scene  of  vital  activity. 


Many  observations  were  made  on  the  contents  of  the  cells 
whilst  undergoing  the  process  of  aggregation,  but  I shall  detail 
only  a few  cases  under  different  heads.  A small  portion  of  a 
leaf  was  cut  off,  placed  under  a high  power,  and  the  glands 
very  gently  pressed  under  a compressor.  In  15  m.  I distinctly 
saw  extremely  minute  spheres  of  protoplasm  aggregating  them- 
selves in  the  purple  fluid ; these  rapidly  increased  in  size,  both 
within  the  cells  of  the  glands  and  of  the  upper  ends  of  the 
pedicels.  Particles  of  glass,  cork,  and  cinders  were  also  placed 
on  the  glands  of  many  tentacles ; in  1 hr.  several  of  them  were 
inflected,  but  after  1 hr.  35  m.  there  was  no  aggregation.  Other 
tentacles  with  these  particles  were  examined  after  8 hrs.,  and 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 


43 


now  all  their  cells  had  undergone  aggregation ; so  had  the  cells 
of  the  exterior  tentacles  which  had  become  inflected  through 
the  irritation  transmitted  from  the  glands  of  the  disc,  on  which 
the  transported  particles  rested.  This  was  likewise  the  case  with 
the  short  tentacles  round  the  margins  of  the  disc,  which  had  not 
as  yet  become  inflected.  This  latter  fact  shows  that  the  pro- 
cess of  aggregation  is  independent  of  the  inflection  of  the  ten- 
tacles, of  which  indeed  we  have  other  and  abundant  e video ce^*' 
Again,  the  exterior  tentacles  on  three  leaves  were  carefully 
examined,  and  found  to  contain  only  homogeneous  purple  fluid ; 
little  bits  of  thread  were  then  placed  on  the  glands  of  three  of 
them,  and  after  22  hrs.  the  purple  fluid  in  their  cells  almost 
down  to  their  bases  was  aggregated  into  innumerable,  spherical, 
elongated,  or  filamentous  masses  of  protoplasm.  The  bits  of 
thread  had  been  carried  some  time  previously  to  the  central 
disc,  and  this  had  caused  all  the  other  tentacles  to  become 
somewhat  inflected;  and  their  cells  had  likewise  undergone 
aggregation,  which  however,  it  should  be  observed,  had  not 
as  yet  extended  down  to  their  bases,  but  was  confined  to  the 
cells  close  beneath  the  glands. 

Not  only  do  repeated  touches  on  the  glands*  and  the  contact 
of  minute  particles  cause  aggregation,  but  if  glands,  without 
being  themselves  injured,  are  cut  off*  from  the  summits  of  the 
pedicels,  this  induces  a moderate  amount  of  aggregation  in  the 
headless  tentacles,  after  they  have  become  inflected.  On  the 
other  hand,  if  glands  are  suddenly  crushed  between  pincers,  as 
was  tried  in  six  cases,  the  tentacles  seem  paralysed  by  so  great 
a shock,  for  they  neither  become  inflected  nor  exhibit  any  signs 
of  aggregation. 

^ Carbonate  of  Ammonia. — Of  all  the  causes  inducing  aggrega- 
tion, that  which,  as  far  as  I have  seen,  acts  the  quickest,  and  is 
the  most  powerful,  is  a solution  of  carbonate  of  ammonia.  What- 
ever its  strength  may  be,  the  glands  are  always  affected  first, 
and  soon  become  quite  opaque,  so  as  to  appear  blacks  For 
instance,  I placed  a leaf  in  a few  drops  of  a strong  solution, 
namely,  of  one  part  to  146  of  water  (or  3 grs.  to  1 oz.),  and 
observed  it  under  a high  power.  All  the  glands  began  to 


* Judging  from  an  account  of 
IVI.  Heckel’s  observations,  which 
I have  only  just  seen  quoted  in 
the  ‘ Gardener’s  Chronicle  ’ (Oct. 
10,  1874),  he  appears  to  have 
observed  a similar  phenomenon  in 


the  stamens  of  Berberis,  after 
they  have  been  excited  by  a 
touch  and  have  moved;  for  he 
says,  “ the  contents  of  each  indi- 
vidual cell  are  collected  together 
in  the  centre  of  the  cavity.” 


44 


DROSERA  ROTUNDIFOLIA. 


Chap.  IIT. 


darken  in  10  s.  (seconds) ; and  in  13  s.  were  conspicnonsly 
darker.  In  1 m.  extremely  small  spherical  masses  of  protoplasm 
could  be  seen  arising  in  the  cells  of  the  pedicels  close  beneath 
the  glands,  as  well  as  in  the  cushions  on  which  the  long- 
headed  marginal  glands  rest.  In  several  cases  the  process 
travelled  down  the  pedicels  for  a length  twice  or  thrice  as  great 
as  that  of  the  glands,  in  about  10  m.  It  was  interesting  to 
observe  the  process  momentarily  arrested  at  each  transverse 
partition  between  two  cells,  and  then  to  see  the  transparent 
contents  of  the  cell  next  below  almost  flashing  into  a cloudy 
mass.  In  the  lower  part  of  the  pedicels,  the  action  proceeded 
slower,  so  that  it  took  about  20  m.  before  the  cells  halfway 
down  the  long  marginal  and  submarginal  tentacles  became 
aggregated. 

/We  may  infer  that  the  carbonate  of  ammonia  is  absorbed  by 
the  glands,  not  only  from  its  action  being  so  rapid,  but  from  its 
effect  being  somewhat  different  from  that  of  other  salts.  As  the 
glands,  when  excited,  secrete  an  acid  belonging  to  the  acetic 
series,  the  carbonate  is  probably  at  once  converted  into  a 
salt  of  this  series;  and  we  shall  presently  see  that  the  acetate 
of  ammonia  causes  aggregation  almost  or  quite  as  energetically 
as  does  the  carbonate.  / If  a few  drops  of  a solution  of  one  part  of 
the  carbonate  to  437  of  water  (or  I gr.  to  I oz.)  be  added  to  the 
purple  fluid  which  exudes  from  crushed  tentacles,  or  to  paper 
stained  by  being  rubbed  with  them,  the  fluid  and  the  paper  are 
changed  into  a pale  dirty  green.  Nevertheless,  some  purple 
colour  could  still  be  detected  after  I hr.  30  m.  within  the  glands 
of  a leaf  left  in  a solution  of  twice  the  above  strength  (viz. 
2 grs.  to  I oz.) ; and  after  24  hrs.  the  cells  of  the  pedicels  close 
beneath  the  glands  still  contained  spheres  of  protoplasm  of  a 
fine  purple  tint.  These  facts  show  that  the  ammonia  had  not 
entered  as  a carbonate,  for  otherwise  the  colour  would  have 
been  discharged.  I have,  however,  sometimes  observed,  espe- 
cially with  the  long-headed  tentacles  on  the  margins  of  very  pale 
leaves  immersed  in  a solution,  that  the  glands  as  well  as  the 
upper  cells  of  the  pedicels  were  discoloured ; and  in  these  cases 
I presume  that  the  unchanged  carbonate  had  been  absorbed. 
The  appearance  above  described,  of  the  aggregating  process 
being  arrested  for  a short  time  at  each  transverse  partition, 
impresses  the  mind  with  the  idea  of  matter  passing  downwards 
from  cell  to  cell.  But  as  the  cells  one  beneath  the  other 
undergo  aggregation  when  inorganic  and  insoluble  particles  are 
placed  on  the  glands,  the  process  must  be,  at  least  in  these 
cases,  one  of  molecular  change,  transmitted  from  the  glands. 


Chap.  111.  THE  PROCESS  OF  AGGREGATION. 


45 


independently  of  the  absorption  of  any  matter.  So  it  may  pos- 
sibly be  in  the  case  of  the  carbonate  of  ammonia.  As,  how- 
ever, the  aggregation  caused  by  this  salt  travels  down  the 
tentacles  at  a quicker  rate  than  when  insoluble  particles  are 
placed  on  the  glands,  it  is  probable  that  ammonia  in  some  form 
is  absorbed  not  only  by  the  glands,  but  passes  down  the 
tentacles. 

Having  examined  a leaf  in  water,  and  found  the  contents  of  the 
cells  homogeneous,  I placed  it  in  a few  drops  of  a solution  of  one 
part  of  the  carbonate  to  437  of  water,  and  attended  to  the  cells 
immediately  beneath  the  glands,  but  did  not  use  a very  high 
power.  No  aggregation  was  visible  in  3 m. ; but  after  15  m. 
small  spheres  of  protoplasm  were  formed,  more  especially 
beneath  the  long-headed  marginal  glands;  the  process,  how- 
ever, in  this  case  took  place  with  unusual  slowness.  In  25  m. 
conspicuous  spherical  masses  were  present  in  the  cells  of  the 
pedicels  for  a length  about  equal  to  that  of  the  glands;  and 
in  3 hrs.  to  that  of  a third  or  half  of  the  whole  tentacle. 

If  tentacles  with  cells  containing  only  very  pale  pink  fluid, 
and  apparently  but  little  protoplasm,  are  placed  in  a few  drops 
of  a weak  solution  of  one  part  of  the  carbonate  to  4375  of 
water  (I  gr.  to  10  oz.),  and  the  highly  transparent  cells  beneath 
the  glands  are  carefully  observed  under  a high  power,  these 
may  be  seen  first  to  become  slightly  cloudy  from  the  formation 
of  numberless,  only  just  perceptible,  granules,  which  rapidly 
grow  larger  either  from  coalescence  or  from  attracting  more 
protoplasm  from  the  surrounding  fluid.  On  one  occasion  I 
chose  a singularly  pale  leaf,  and  gave  it,  whilst  under  the 
microscope,  a single  drop  of  a stronger  solution  of  one  part  to 
437  of  water;  in  this  case  the  contents  of  the  cells  did  not 
become  cloudy,  but  after  10  m.  minute  irregular  granules  of 
protoplasm  could  be  detected,  which  soon  increased  into 
irregular  masses  and  globules  of  a greenish  or  very  pale  purple 
tint ; but  these  never  formed  perfect  spheres,  though  incessantly 
changing  their  shapes  and  positions. 

With  moderately  red  leaves  the  first  effect  of  a solution  of  the 
carbonate  generally  is  the  formation  of  two  or  three,  or  of 
several,  extremely  minute  purple  spheres  which  rapidly  increase 
in  size.  To  give  an  idea  of  the  rate  at  which  such  spheres 
increase  in  size,  I may  mention  that  a rather  pale  purple  leaf 
placed  under  a slip  of  glass  was  given  a drop  of  a solution  of 
one  part  to  292  of  water,  and  in  13  m.  a few  minute  spheres  of 
protoplasm  were  formed ; one  of  these,  after  2 hrs.  30  m.,  was 
about  two  thirds  of  the  diameter  of  the  cell.  After  4 hrs.  25  m. 


46 


DROSERA  ROTUNDIFOLIA. 


Chap.  HI. 


it  nearly  equalled  the  cell  in  diameter;  and  a second  spheir^ 
about  half  as  large  as  the  first,  together  with  a few  other 
minute  ones,  were  formed.  After  6 hrs.  the  fluid  in  which  these 
spheres  floated  was  almost  colourless.  After  8 hrs.  35  m.  (always 
reckoning  from  the  time  when  the  solution  was  first  added)  four 
new  minute  spheres  had  appeared.  Next  morning,  after  22  hrs., 
there  were,  besides  the  two  large  spheres,  seven  smaller  ones, 
floating  in,  absolutely  colourless  fluid,  in  which  some  flocculent 
greenish  matter  was  suspended. 

At  the  commencement  of  the  process  of  aggregation,  more 
especially  in  dark  red  leaves,  the  contents  of  the  cells  often 
present  a different  appearance,  as  if  the  layer  of  protoplasm 
(primordial  utricle)  which  lines  the  cells  had  separated  itself 
and  shrunk  from  the  walls ; an  irregularly  shaped  purple  bag 
being  thus  formed.  Other  fluids,  besides  a solution  of  the  car- 
bonate, for  instance  an  infusion  of  raw  meat,  produce  this  same 
effect.  But  the  appearance  of  the  primordial  utricle  shrinking 
from  the  walls  is  certainly  false ; * for  before  giving  the  solution, 
I saw  on  several  occasions  that  the  walls  were  lined  with  colour- 
less flowing  protoplasm,  and  after  the  bag-like  masses  were 
formed,  the  protoplasm  was  still  flowing  along  the  walls  in  a 
conspicuous  manner,  even  more  so  than  before.  It  appeared 
indeed  as  if  the  stream  of  protoplasm  was  strengthened  by  the 
action  of  the  carbonate,  but  it  was  impossible  to  ascertain 
whether  this  was  really  the  case.  The  bag-like  masses,  when 
once  formed,  soon  begin  to  glide  slowly  round  the  cells,  some- 
times sending  out  projections  which  separate  into  little  spheres ; 
other  spheres  appear  in  the  fluid  surrounding  the  hags,  and 
these  travel  much  more  quickly.  That  the  small  spheres  are 
separate  is  often  shown  by  sometimes  one  and  then  another 
travelling  in  advance,  and  sometimes  they  revolve  round  each 
other.  I have  occasionally  seen  spheres  of  this  kind  proceeding 
up  and  down  the  same  side  of  a cell,  instead  of  round  it.  The 
bag-like  masses  after  a time  generally  divide  into  two  rounded 
or  oval  masses,  and  these  undergo  the  changes  shown  in  figs.  7 
and  8.  At  other  times  spheres  appear  within  the  bags;  and 
these  coalesce  and  separate  in  an  endless  cycle  of  change. 

After  leaves  have  been  left  for  several  hours  in  a solution  of 
the  carbonate,  and  complete  aggregation  has  been  effected,  the 


* With  other  plants  I have  caused  by  a solution  of  carbonate 

often  seen  what  appears  to  be  a of  ammonia,  as  likewise  follows 

true  shrinking  of  the  primordial  . from  mechanical  injuries, 
utricle  from  tiie  walls  of  the  cells, 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 


47 


stream  of  protoplasm  on  the  walls  of  the  cells  ceases  to  be 
visible ; I observed  this  fact  repeatedly,  but  will  give  only  one 
instance.  A pale  purple  leaf  was  placed  in  a few  drops  of  a 
solution  of  one  part  to  292  of  water,  and  in  2 hrs.  some  fine 
purple  spheres  were  formed  in  the  upper  cells  of  the  pedicels, 
the  stream  of  protoplasm  round  their  walls  being  still  quite 
distinct;  but  after  an  additional  4 hrs.,  during  which  time 
many  more  spheres  were  formed,  the  stream  was  no  longer 
distinguishable  on  the  most  careful  examination;  and  this  no 
doubt  was  due  to  the  contained  granules  having  become  united 
with  the  spheres,  so  that  nothing  was  left  by  which  the  move- 
ment of  the  limpid  protoplasm  could  be  perceived.  But  minute 
free  spheres  still  travelled  up  and  down  the  cells,  showing  that 
there  was  still  a current.  So  it  was  next  morning,  after  22  hrs., 
by  which  time  some  new  minute  spheres  had  been  formed; 
these  oscillated  from  side  to  side  and  changed  their  positions, 
proving  that  the  current  had  not  ceased,  though  no  stream  of 
protoplasm  was  visible.  On  another  occasion,  however,  a 
stream  was  seen  flowing  round  the  cell-walls  of  a vigorous, 
dark-coloured  leaf,  after  it  had  been  left  for  24  hrs.  in  a rather 
stronger  solution,  namely,  of  one  part  of  the  carbonate  to  218  of 
water.  This  leaf,  therefore,  was  not  much  or  at  all  injured  by 
an  immersion  for  this  length  of  time  in  the  above  solution  of 
two  grains  to  the  ounce ; and  on  being  afterwards  left  for  24  hrs. 
in  water,  the  aggregated  masses  in  many  of  the  cells  were  re- 
dissolved, in  the  same  manner  as  occurs  with  leaves  in  a state  of 
nature  when  they  re-expand  after  having  caught  insects. 

In  a leaf  which  had  been  left  for  22  hrs.  in  a solution  of  one 
part  of  the  carbonate  to  292  of  water,  some  spheres  of  proto- 
plasm (formed  by  the  self- division  of  a bag-like  mass)  were 
gently  pressed  beneath  a covering  glass,  and  then  examined 
under  a high  power.  They  were  now  distinctly  divided  by 
well-defined  radiating  fissures,  or  were  broken  up  into  separate 
fragments  with  sharp  edges ; and  they  were  solid  to  the  centre. 
In  the  larger  broken  spheres  the  central  part  was  more  opaque, 
darker -coloured,  and  less  brittle  than  the  exterior ; the  latter 
alone  being  in  some  cases  penetrated  by  the  fissures.  In  many 
of  the  spheres  the  line  of  separation  between  the  outer  and 
inner  parts  was  tolerably  well  defined.  The  outer  parts  were  of 
. exactly  the  same  very  pale  purple  tint,  as  that  of  the  last 
formed  smaller  spheres;  and  these  latter  did  not  include  any 
darker  central  core. 

/ From  these  several  facts  we  may  conclude  that  when  vigorous 
dark-coloured  leaves  are  subjected  to  the  action  of  carbonate  of 


48 


DROSERA  ROTUNDIFOLIA. 


Chap.  Ill 


ammonia,  the  fluid  within  the  cells  of  the  tentacles  often  aggre- 
gates exteriorly  into  coherent  viscid  matter,  forming  a kind  of 
bag/  Small  spheres  sometimes  appear  within  this  bag,  and  the 
whole  generally  soon  divides  into  two  or  more  spheres,  which 
repeatedly  coalesce  and  redivide.  After  a longer  or  shorter 
time  the  granules  in  the  colourless  layer  of  protoplasm,  which 
flows  round  the  walls,  are  drawn  to  and  unite  with  the  larger 
spheres,  or  form  small  independent  spheres ; these  latter  being  of 
a much  paler  colour,  and  more  brittle  than  the  flrst  aggregated 
masses.  After  the  granules  of  protoplasm  have  been  thus 
attracted,  the  layer  of  flowing  protoplasm  can  no  longer  be  dis- 
tinguished, though  a current  of  limpid  fluid  still  flows  round 
the  walls. 

If  a leaf  is  immersed  in  a very  strong,  almost  concentrated, 
solution  of  carbonate  of  ammonia,  the  glands  are  instantly 
blackened,  and  they  secrete  copiously ; but  no  movement  of  the 
tentacles  ensues.  Two  leaves  thus  treated  became  after  1 hr. 
flaccid,  and  seemed  killed ; all  the  cells  in  their  tentacles  con- 
tained spheres  of  protoplasm,  but  these  were  small  and  dis- 
coloured. Two  other  leaves  were  placed  in  a solution  not  quite 
so  strong,  and  there  was  well-marked  aggregation  in  30  m. 
After  24  hrs.  the  spherical  or  more  commonly  oblong  masses  of 
protoplasm  became  opaque  and  granular,  instead  of  being  as 
usual  translucent;  and  in  the  lower  cells  there  were  only 
innumerable  minute  spherical  granules.  It  was  evident  that 
the  strength  of  the  solution  had  interfered  with  the  completion 
of  the  process,  as  we  shall  see  likewise  follows  from  too  great 
heat. 

All  the  foregoing  observations  relate  to  the  exterior  tentacles, 
which  are  of  a purple  colour;  but  the  green  pedicels  of  the 
short  central  tentacles  are  acted  on  by  the  carbonate,  and  by 
an  infusion  of  raw  meat,  in  exactly  the  same  manner,  with  the 
sole  difference  that  the  aggregated  masses  are  of  a greenish 
colour ; so  that  the  process  is  in  no  way  dependent  on  the 
colour  of  the  fluid  within  the  cells. 

Finally,  the  most  remarkable  fact  with  respect  to  this  salt  is 
the  extraordinary  small  amount  which  suffices  to  cause  aggre- 
gation. Full  details  will  be  given  in  the  seventh  chapter,  and 
/here  it  will  be  enough  to  say  that  with  a sensitive  leaf  the 
absorption  by  a gland  of  ^ grain  (*000482  mgr.)  is 

enough  to  cause  in  the  course  of  one  hour  well-marked  aggrega- 
tion in  the  cells  immediately  beneath  the  gland.  / 

Tlie  Effects  of  certain  other  Salts  and  Fluids. — Two  leaves  were 
placed  in  a solution  of  one  part  of  acetate  of  ammonia  to  about 


Chap.  111. 


THE  PROCESS  OF  AGGREGATION^. 


49 


146  of  water,  and  were  acted  on  quite  as  energetically,  but 
perhaps  not  quite  so  quickly,  as  by  the  carbonate.  After  10  m. 
the  glands  were  black,  and  in  the  cells  beneath  them  there  were 
traces  of  aggregation,  which  after  15  m.  was  well  marked,  extend- 
ing down  the  tentacles  for  a length  equal  to  that  of  the  glands. 
After  2 hrs.  the  contents  of  almost  all  the  cells  in  all  the  ten- 
tacles were  broken  up  into  masses  of  protoplasm.  A leaf  was 
immersed  in  a solution  of  one  part  of  oxalate  of  ammonia  to 
146  of  water;  and  after  24  m.  some,  but  not  a conspicuous, 
change  could  be  seen  within  the  cells  beneath  the  glands. 
After  47  m.  plenty  of  spherical  masses  of  protoplasm  were 
formed,  and  these  extended  down  the  tentacles  for  about  the 
length  of  the  glands.  This  salt,  therefore,  does  not  act  so 
quickly  as  the  carbonate.  With  respect  to  the  citrate  of  am- 
monia, a leaf  was  placed  in  a little  solution  of  the  above 
strength,  and  there  was  not  even  a trace  of  aggregation  in  the 
cells  beneath  the  glands,  until  56  m.  had  elapsed ; but  it  was 
well  marked  after  2 hrs.  20  m.  On  another  occasion  a leaf 
was  placed  in  a stronger  solution,  of  one  part  of  the  citrate  to 
109  of  water  (4  grs.  to  1 oz.),  and  at  the  same  time  another 
leaf  in  a solution  of  the  carbonate  of  the  same  strength.  The 
glands  of  the  latter  were  blackened  in  less  than  2 m.,  and 
after  1 hr.  45  m.  the  aggregated  masses,  which  were  spherical 
and  very  dark-coloured,  extended  down  all  the  tentacles,  for 
between  half  and  two-thirds  of  their  lengths ; whereas  in  the 
leaf  immersed  in  the  citrate  the  glands,  after  30  m.,  were  of 
a dark  red,  and  the  aggregated  masses  in  the  cells  beneath  them 
pink  and  elongated.  After  1 hr.  45  m.  these  masses  extended 
down  for  only  about  one-fifth  or  one -fourth  of  the  length  of  the 
tentacles. 

Two  leaves  were  placed,  each  in  ten  minims  of  a solution  of 
one  part  of  nitrate  of  ammonia  to  5250  of  water  (1  gr.  to 
12  oz.),  so  that  each  leaf  received  of  a grain  (*1124  mgr.). 
This  quantity  caused  all  the  tentacles  to  be  inflected,  but  after 
24  hrs.  there  was  only  a trace  of  aggregation.  One  of  these 
same  leaves  was  then  placed  in  a weak  solution  of  the  car- 
bonate, and  after  1 hr.  45  m.  the  tentacles  for  half  their  lengths 
showed  an  astonishing  degree  of  aggregation.  Two  other 
leaves  were  then  placed  in  a much  stronger  solution  of  one  part 
of  the  nitrate  to  146  of  water  (3  grs.  to  1 oz.) ; in  one  of  these 
there  was  no  marked  change  after  3 hrs.;  but  in  the  other 
there  was  a trace  of  aggregation  after  52  m.,  and  this  was 
plainly  marked  after  1 hr.  22  m , but  even  after  2 hrs.  12  m. 
there  was  certainly  not  more  aggregation  than  would  have  fol- 


50 


DKOSERA  ROTUNDIFOLIA. 


Chap.  III. 


lowed  from  an  immersion  of  from  5 m.  to  10  m.  in  an  equally 
strong  solution  of  the  carbonate. 

Lastly,  a leaf  was  placed  in  thirty  minims  of  a solution  of 
one  part  of  phosphate  of  ammonia  to  43,750  of  water  (1  gr.  to 
100  oz.),  so  that  it  received  YeVo  ^ grain  (*04079  mgr.);  this 
soon  caused  the  tentacles  to  be  strongly  inflected;  and  after 
24  hrs.  the  contents  of  the  cells  were  aggregated  into  oval 
and  irregularly  globular  masses,  with  a conspicuous  current  of 
protoplasm  flowing  round  the  walls.  But  after  so  long  an 
interval  aggregation  would  have  ensued,  whatever  had  caused 
inflection. 

Only  a few  other  salts,  besides  those  of  ammonia,  were  tried 
in  relation  to  the  process  of  aggregation.  A leaf  was  placed  in 
a solution  of  one  part  of  chloride  of  sodium  to  218  of  water,  and 
after  1 hr.  the  contents  of  the  cells  were  aggregated  into  small, 
irregularly  globular,  brownish  masses ; these  after  2 hrs.  were 
almost  disintegrated  and  pulpy.  It  was  evident  that  the  proto- 
plasm had  been  injuriously  affected ; and  soon  afterwards  some 
of  the  cells  appeared  quite  empty.  These  effects  differ  alto- 
gether from  those  produced  by  the  several  salts  of  ammonia, 
as  well  as  by  various  organic  fluids,  and  by  inorganic  particles 
placed  on  the  glands,  A solution  of  the  same  strength  of  car- 
bonate of  soda  and  carbonate  of  potash  acted  in  nearly  the  same 
manner  as  the  chloride ; and  here  again,  after  2 hrs.  30  m.,  the 
outer  cells  of  some  of  the  glands  had  emptied  themselves  of 
their  brown  pulpy  contents.  We  shall  see  in  the  eighth 
chapter  that  solutions  of  several  salts  of  soda  of  half  the  above 
strength  cause  inflection,  but  do  not  injure  the  leaves.  Weak 
solutions  of  sulphate  of  quinine,  of  nicotine,  camphor,  poison  of 
the  cobra,  &c.,  soon  induce  well-marked  aggregation ; whereas 
certain  other  substances  (for  instance,  a solution  of  curare) 
have  no  such  tendency. 

/ Many  acids,  though  much  diluted,  are  poisonous ; and  though, 
as  will  be  shown  in  the  eighth  chapter,  they  cause  the  ten- 
tacles to  bend,  they  do  not  excite  true  aggregation./  Thus  leaves 
were  placed  in  a solution  of  one  part  of  benzoic  acid  to  437  of 
water ; and  in  15  m.  the  purple  fluid  within  the  cells  had  shrunk 
a little  from  the  walls,  yet  when  carefully  examined  after  1 hr. 
20  m.,  there  was  no  true  aggregation ; and  after  24  hrs.  the  leaf 
was  evidently  dead.  Other  leaves  in  iodic  acid,  diluted  to  tht 
same  degree,  showed  after  2 hrs.  15  m.  the  same  shrunken 
appearance  of  the  purple  fluid  within  the  cells ; and  these, 
after  6 hrs.  15  m.,  were  seen  under  a high  power  to  be  filled 
with  excessively  minute  spheres  of  dull  reddish  protoplasm, 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 


51 


which  by  the  next  morning,  after  24  hrs.,  had  almost  dis- 
appeared, the  leaf  being  evidently  dead.  Nor  was  there  any  true 
aggregation  in  leaves  immersed  in  propionic  acid  of  the  same 
strength;  but  in  this  case  the  protoplasm  was  collected  in 
irregular  masses  towards  the  bases  of  the  lower  cells  of  the 
tentacles. 

A filtered  infusion  of  raw  meat  induces  strong  aggregation, 
but  not  very  quickly.  In  one  leaf  thus  immersed  there  was  a 
little  aggregation  after  1 hr.  20  m.,  and  in  another  after  1 hr. 
60  m.  With  other  leaves  a considerably  longer  time  was  re- 
quired : for  instance,  one  immersed  for  5 hrs.  showed  no  aggre- 
gation, but  was  plainly  acted  on  in  5 m.,  when  placed  in  a few 
drops  of  a solution  of  one  part  of  carbonate  of  ammonia  to  146 
of  water.  Some  leaves  were  left  in  the  infusion  for  24  hrs., 
and  these  became  aggregated  to  a wonderful  degree,  so  that 
the  inflected  tentacles  presented  to  the  naked  eye  a plainly 
mottled  appearance.  The  little  masses  of  purple  protoplasm 
were  generally  oval  or  beaded,  and  not  nearly  so  often  spherical 
as  in  the  case  of  leaves  subjected  to  carbonate  of  ammonia. 
They  underwent  incessant  changes  of  form ; and  the  current  of 
colourless  protoplasm  round  the  walls  was  conspicuously  plain 
after  an  immersion  of  25  hrs.  /Raw  meat  is  too  powerful  a 
stimulant,  and  even  small  bits  generally  injure,  and  sometimes 
lull,  the  leaves  to  which  they  are  given : the  aggregated  masses 
of  protoplasm  become  dingy  or  almost  colourless,  and  present 
an  unusual  granular  appearance,  as  is  likewise  the  case  with 
leaves  which  have  been  immersed  in  a very  strong  solution  of 
carbonate  of  ammonia/  A leaf  placed  in  milk  had  the  contents 
of  its  cells  somewhat  aggregated  in  1 hr.  Two  other  leaves, 
one  immersed  in  human  saliva  for  2 hrs.  30  m.,  and  another 
in  unboiled  white  of  egg  for  1 hr.  30  m.,  were  not  acted  on  in 
this  manner;  though  they  undoubtedly  would  have  been  so, 
had  more  time  been  allowed.  These  same  two  leaves,  on  being 
afterwards  placed  in  a solution  of  carbonate  of  ammonia  (3  grs. 
to  1 oz.),  had  their  cells  aggregated,  the  one  in  10  m.  and  the 
other  in  5 m. 

Several  leaves  were  left  for  4 hrs.  30  m.  in  a solution  of  one 
part  of  white  sugar  to  146  of  water,  and  no  aggregation  ensued  * 
on  being  placed  in  a solution  of  this  same  strength  of  carbonate 
of  ammonia,  they  were  acted  on  in  5 m. ; as  was  likewise  a leaf 
which  had  been  left  for  1 hr.  45  m.  in  a moderately  thick  solu- 
tion of  gum  arabic.  Several  other  leaves  were  immersed  for 
some  hours  in  denser  solutions  of  sugar,  gum,  and  starch,  and 
they  had  the  contents  of  their  cells  greatly  aggregated.  This 


52 


DROSERA  ROTUNDIFOLIA. 


Chap.  111. 


effect  may  be  attributed  to  exosmose;  for  the  leaves  in  the 
syrup  became  quite  flaccid,  and  those  in  the  gum  and  starch 
somewhat  flaccid,  with  their  tentacles  twisted  about  in  the 
most  irregular  manner,  the  longer  ones  like  corkscrews.  We 
shall  hereafter  see  that  solutions  of  these  substances,  when 
placed  on  the  discs  of  leaves,  do  not  incite  inflection.  Particles 
of  soft  sugar  were  added  to  the  secretion  round  several  glands 
and  were  soon  dissolved,  causing  a great  increase  of  the  secre- 
tion, no  doubt  by  exosmose ; and  after  24  hrs.  the  cells  showed 
a certain  amount  of  aggregation,  though  the  tentacles  were 
not  inflected.  Glycerine  causes  in  a few  minutes  well-pro- 
nounced aggregation,  commencing  as  usual  within  the  glands 
and  then  travelling  down  the  tentacles;  and  this  I presume 
may  be  attributed  to  the  strong  attraction  of  this  substance 
for  water.  Immersion  for  several  hours  in  water  causes  some 
degree  of  aggregation.  Twenty  leaves  were  first  carefully 
examined,  and  re-examined  after  having  been  left  immersed 
in  distilled  water  for  various  periods,  with  the  following  results. 
It  is  rare  to  find  even  a trace  of  aggregation  until  4 or  5 
and  generally  not  until  several  more  hours  have  elapsed. 
When  however  a leaf  becomes  quickly  inflected  in  water,  as 
sometimes  happens,  especially  during  very  warm  weather, 
aggregation  may  occur  in  little  over  I hr.  In  all  cases 
leaves  left;  in  water  for  more  than  24  hrs.  have  their  glands 
blackened,  which  shows  that  their  contents  are  aggregated; 
and  in  the  specimens  which  were  carefully  examined,  there 
was  fairly  well-marked  aggregation  in  the  upper  cells  of  the 
pedicels.  These  trials  were  made  with  cut-off  leaves,  and  it 
occurred  to  me  that  this  circumstance  might  influence  the 
result,  as  the  footstalks  would  not  perhaps  absorb  water  quickly 
enough  to  supply  the  glands  as  they  continued  to  secrete. 
But  this  view  was  proved  erroneous,  for  a plant  with  uninjured 
roots,  bearing  four  leaves,  was  submerged  in  distilled  water  for 
47  hrs.,  and  the  glands  were  blackened,  though  the  tentacles 
were  very  little  inflected.  In  one  of  these  leaves  there  was  only 
a slight  degree  of  aggregation  in  the  tentacles;  in  the  second 
rather  more,  the  purple  contents  of  the  cells  being  a little 
separated  from  the  walls ; in  the  third  and  fourth,  which  were 
pale  leaves,  the  aggregation  in  the  upper  parts  of  the  pedicels 
was  well  marked.  In  these  leaves  the  little  masses  of  proto- 
plasm, many  of  which  were  oval,  slowly  changed  their  forms 
and  positions ; so  that  a submergence  for  47  hrs.  had  not  killed 
the  protoplasm.  In  a previous  trial  with  a submerged  plant, 
the  tentacles  were  not  in  the  least  inflected. 


53 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 

'^Heat  induces  aggregation^  A leaf,  with  the  cells  of  the 
tentacles  containing  only  homogeneous  fluid,  was  waved  about 
for  1 m.  in  water  at  130°  Fahr.  (54:°*4  Cent.),  and  was  then 
examined  under  the  microscope  as  quickly  as  possible,  that 
is  in  2 m.  or  3 m. ; and  by  this  time  the  contents  of  the 
cells  had  undergone  some  degree  of  aggregation.  A second  leaf 
was  waved  for  2 m.  in  water  at  125°  (51°-6  Cent.)  and  quickly 
examined  as  before ; the  tentacles  were  well  inflected ; the 
purple  fluid  in  all  the  cells  had  shrunk  a little  from  the  walls, 
and  contained  many  oval  and  elongated  masses  of  protoplasm, 
with  a few  minute  spheres.  A third  leaf  was  left  in  water  at 
125°,  until  it  cooled,  and  when  examined  after  1 hr.  45  m.,  the 
inflected  tentacles  showed  some  aggregation,  which  became 
after  3 hrs.  more  strongly  marked,  but  did  not  subsequently 
increase.  Lastly,  a leaf  was  waved  for  1 m.  in  water  at  120° 
(48°‘8  Cent.)  and  then  left  for  1 hr.  26  m.  in  cold  water ; the 
tentacles  were  but  little  inflected,  and  there  was  only  here  and 
there  a trace  of  aggregation.  In  all  these  and  other  trials 
with  warm  water  the  protoplasm  showed  much  less  tendency 
to  aggregate  into  spherical  masses  than  when  excited  by  car- 
bonate of  ammonia. 

Redissolution  of  the  Aggregated  Masses  of  Protoplasm,— As  soon 
as  tentacles  which  have  clasped  an  insect  or  any  inorganic 
object,  or  have  been  in  any  way  excited,  have  fully  re-expanded, 
the  aggregated  masses  of  protoplasm  are  redissolved  and  dis- 
appear ; the  cells  being  now  refilled  with  homogeneous  purple 
fluid  as  they  were  before  the  tentacles  were  inflected.  The 
process  of  redissolution  in  all  cases  commences  at  the  bases  of  the 
tentacles,  and  proceeds  up  them  towards  the  glands.  In  old 
leaves,  however,  especially  in  those  which  have  been  several 
times  in  action,  the  protoplasm  in  the  uppermost  cells  of  the 
pedicels  remains  in  a permanently  more  or  less  aggregated  con- 
dition./ In  order  to  observe  the  process  of  redissolution,  the 
following  observations  were  made  : a leaf  was  left  for  24  hrs.  in 
a little  solution  of  one  part  of  carbonate  of  ammonia  to  218  of 
water,  and  the  protoplasm  was  as  usual  aggregated  into  number- 
less purple  spheres,  which  were  incessantly  changing  their 
forms.  The  leaf  was  then  washed  and  placed  in  distilled  water, 
and  after  3 hrs.  15  m.  some  few  of  the  spheres  began  to  show  by 
their  less  clearly  defined  edges  signs  of  redissolution.  After 
9 hrs.  many  of  them  had  become  elongated,  and  the  surround- 
ing fluid  in  the  cells  was  slightly  more  coloured,  showing 
plainly  that  redissolution  had  commenced.  After  24  hrs., 
though  many  cells  still  contained  spheres,  here  and  there  one 


54 


DROSEKA  ROT  UNDIFOLIA. 


Chap.  III. 


could  be  seen  filled  with  purple  fluid,  without  a vestige  of 
aggregated  protoplasm ; the  whole  having  been  redissolved.  A 
leaf  with  aggregated  masses,  caused  by  its  having  been  waved 
for  2 m.  in  water  at  the  temperature  of  125°  Fahr.,  was  left  in 
cold  water,  and  after  11  hrs.  the  protoplasm  showed  traces 
of  incipient  redissolution.  When  again  examined  three  days 
after  its  immersion  in  the  warm  water,  there  was  a conspicuous 
difference,  though  the  protoplasm  was  still  somewhat  aggre- 
gated. Another  leaf,  with  the  contents  of  all  the  cells  strongly 
aggregated  from  the  action  of  a weak  solution  of  phosphate  of 
ammonia,  was  left  for  between  three  and  four  days  in  a mixture 
(known  to  be  innocuous)  of  one  drachm  of  alcohol  to  eight 
drachms  of  water,  and  when  re-examined  every  trace  of  aggre- 
gation had  disappeared,  the  cells  being  now  filled  with  homo- 
geneous fluid. 

We  have  seen  that  leaves  immersed  for  some  hours  in  dense 
solutions  of  sugar,  gum,  and  starch,  have  the  contents  of  their 
cells  greatly  aggregated,  and  are  rendered  more  or  less  flaccid, 
with  the  tentacles  irregularly  contorted.  These  leaves,  after 
being  left  for  four  days  in  distilled  water,  became  less  flaccid, 
with  their  tentacles  partially  re-expanded,  and  the  aggre- 
gated masses  of  protoplasm  were  partially  redissolved.  A leaf 
with  its  tentacles  closely  clasped  over  a fly,  and  with  the  con- 
tents of  the  cells  strongly  aggregated,  was  placed  in  a little 
sherry  wine;  after  2 hrs.  several  of  the  tentacles  had  re- 
expanded, and  the  others  could  by  a mere  touch  be  pushed  back 
into  their  properly  expanded  positions,  and  now  all  traces  of 
aggregation  had  disappeared,  the  cells  being  filled  with  perfectly 
homogeneous  pink  fluid.  -'The  redissolution  in  these  cases  may, 
I presume,  be  attributed  to  end  osmose./ 


On  the  Proximate  Causes  of  the  Process  of  Aggregation. 

* As  most  of  the  stimulants  which  cause  the  inflection 
of  the  tentacles  likewise  induce  aggregation  in  the 
contents  of  their  cells,  this  latter  process  might  be 
thought  to  be  the  direct  result  of  inflection ; but  this 
is  not  the  case.  If  leaves  are  placed  in  rather  strong 
solutions  of  carbonate  of  ammonia,  for  instance  of 
three  or  four,  and  even  sometimes  of  only  two  grains 
to  the  ounce  of  water  (i.e.  one  part  to  109,  or  146,  or 


Chap.  III. 


THE  PROCESS  OF  AGGREGATION. 


55 


218,  of  water),  the  tentacles  are  paralysed,  and  do  not 
become  inflected,  yet  they  soon  exhibit  strongly 
marked  aggregation.  Moreover,  the  short  central 
tentacles  of  a leaf  which  has  been  immersed  in  a 
weak  solution  of  any  salt  of  ammonia,  or  in  any 
nitrogenous  organic  fluid,  do  not  become  in  the  least 
inflected;  nevertheless  they  exhibit  all  the  pheno- 
mena of  aggregation.  On  the  other  hand,  several 
acids  cause  strongly  pronounced  inflection,  but  no 
aggregation."^ 

'It  is  an  important  fact  that  when  an  organic  or  in- 
organic object  is  placed  on  the  glands  of  the  disc, 
and  the  exterior  tentacles  are  thus  caused  to  bend 
inwards,  not  only  is  the  secretion  from  the  glands  of 
the  latter  increased  in  quantity  and  rendered  acid, 
but  the  contents  of  the  cells  of  their  pedicels  become 
aggregated.  The  process  always  commences  in  the 
glands,  although  these  have  not  as  yet  touched  any 
object.  Some  force  or  influence  must,  therefore,  be 
transmitted  from  the  central  glands  to  the  exterior 
tentacles,  first  to  near  their  bases  causing  this  part  to 
bend,  and  next  to  the  glands  causing  them  to  secrete 
more  copiously.  After  a short  time  the  glands,  thus 
indirectly  excited,  transmit  or  reflect  some  influence 
down  their  own  pedicels,  inducing  aggregation  in  cel] 
beneath  cell  to  their  bases.  ^ 

It  seems  at  first  sight  a probable  view  that  aggrega- 
tion is  due  to  the  glands  being  excited  to  secrete  more 
copiously,  so  that  sufficient  fluid  is  not  left  in  their 
cells,  and  in  the  cells  of  the  pedicels,  to  hold  the 
protoplasm  in  solution.  In  favour  of  this  view  is  the 
fact  that  aggregation  follows  the  inflection  of  the 
tentacles,  and  during  the  movement  the  glands  gener- 
ally, or,  as  I believe,  always,  secrete  more  copiously 
than  they  did  before.  Again,  during  the  re-expansion 


56 


DROSEEA  ROTUNDIFOLIA. 


Chap.  Ill 


of  the  tentacles,  the  glands  secrete  less  freely,  or  quite 
cease  to  secrete,  and  the  aggregated  masses  of  proto- 
plasm are  then  redissolved. Moreover,  when  leaves 
are  immersed  in  dense  vegetable  solutions,  or  in 
glycerine,  the  fluid  within  the  gland-cells  passes  out- 
wards, and  there  is  aggregation ; and  when  the  leaves 
are  afterwards  immersed  in  water,  or  in  an  innocuous 
fluid  of  less  specific  gravity  than  water,  the  protoplasm 
is  redissolved,  and  this,  no  doubt,  is  due  to  endosmose. 

/Opposed  to  this  view,  that  aggregation  is  caused  by 
the  outward  passage  of  fluid  from  the  cells,  are  the 
following  facts.  There  seems  no  close  relation  between 
the  degree  of  increased  secretion  and  that  of  aggre- 
gation./ Thus  a particle  of  sugar  added  to  the  secre- 
tion round  a gland  causes  a much  greater  increase  of 
secretion,  and  much  less  aggregation,  than  does  a 
particle  of  carbonate  of  ammonia  given  in  the  samo 
manner.  It  does  not  appear  probable  that  pure  water 
would  cause  much  exosmose,  and  yet  aggregation 
often  follows  from  an  immersion  in  water  of  between 
16  hrs.  and  24  hrs.,  and  always  after  from  24  hrs.  to 
48  hrs.  Still  less  probable  is  it  that  water  at  a tempe- 
rature of  from  125^^  to  130°  Fahr.  (51°*6  to  54°*4  Cent.) 
should  cause  fluid  to  pass,  not  only  from  the  glands, 
but  from  all  the  cells  of  the  tentacles  down  to  their 
bases,  so  quickly  that  aggregation  is  induced  within 
2 m.  or  3 m.  f Another  strong  argument  against 
this  view  is,  that,  after  complete  aggregation,  the 
spheres  and  oval  masses  of  protoplasm  float  about 
in  an  abundant  supply  of  thin  colourless  fluid ; so 
that  at  least  the  latter  stages  of  the  process  cannot 
be  due  to  the  want  of  fluid  to  hold  the  protoplasm 
in  solution.  I There  is  still  stronger  evidence  that 
aggregation  is  independent  of  secretion; (for  the  pa- 
pillae, described  in  the  first  chapter,  with  which  the 


Ohap.  hi.  the  process  of  aggregation. 


57 


leaves  are  studded  are  not  glandular,  and  do  not 
secrete,  yet  they  rapidly  absorb  carbonate  of  ammonia 
or  an  infusion  of  raw  meat,  and  their  contents  then 
quickly  undergo  aggregation,  which  afterwards  spreads 
into  the  cells  of  the/ surrounding  tissues.  We  shall 
hereafter  see  that  the  purple  fluid  within  the  sensi- 
tive filaments  of  Dionaea,  which  do  not  secrete,  like- 
wise undergoes  aggregation  from  the  action  of  a weak 
solution  of  carbonate  of  ammonia. 

/ The  process  of  aggregation  is  a vital  one ; by  which 
I mean  that  the  contents  of  the  cells  must  be  alive 
and  uninjured  to  be  thus  affected,  and  they  must  be  in 
an  oxygenated  condition  for  the  transmission  of  the 
process  at  the  proper  rate.  ! Some  tentacles  in  a 
drop  of  water  were  strongly  pressed  beneath  a slip  of 
glass;  many  of  the  cells  were  ruptured,  and  pulpy 
matter  of  a purple  colour,  with  granules  of  all  sizes 
and  shapes,  exuded,  but  hardly  any  of  the  cells  were 
completely  emptied.  I then  added  a minute  drop  of 
a solution  of  one  part  of  carbonate  of  ammonia  to 
109  of  water,  and  after  1 hr.  examined  the  specimens. 
Here  and  there  a few  cells,  both  in  the  glands  and  in 
the  pedicels,  had  escaped  being  ruptured,  and  their 
contents  were  well  aggregated  into  spheres  which  were 
constantly  changing  their  forms  and  positions,  and  a 
current  could  still  be  seen  flowing  along  the  walls ; 
so  that  the  protoplasm  was  alive.  On  the  other  hand, 
the  exuded  matter,  which  was  now  almost  colourless 
instead  of  being  purple,  did  not  exhibit  a trace  of 
aggregation.  Nor  was  there  a trace  in  the  many 
cells  which  were  ruptured,  but  which  had  not  been 
completely  emptied  of  their  contents.  Though  I 
looked  carefully,  no  signs  of  a current  could  be  seen 
within  these  ruptured  cells.  They  had  evidently  been 
killed  by  the  pressure ; and  the  matter  which  they 


58 


DROSERA  ROTUNDIFOLIA. 


Chap.  IIL 


still  contained  did  not  undergo  aggregation  any  more 
than  that  which  had  exuded.  In  these  specimens,  as 
I may  add,  the  individuality  of  the  life  of  each  cell 
was  well  illustrated. 

' A full  account  will  be  given  in  the  next  chapter  of 
the  effects  of  heat  on  the  leaves,  and  I need  here  only 
state  that  leaves  immersed  for  a short  time  in  water  at 
a temperature  of  120^^  Fahr.  (48°*8  Cent.),  which,  as  we 
have  seen,  does  not  immediately  induce  aggregation, 
were  then  placed  in  a few  drops  of  a strong  solution 
of  one  part  of  carbonate  of  ammonia  to  109  of  water, 
and  became  finely  aggregated.  On  the  other  hand, 
leaves,  after  an  immersion  in  water  at  150°  (65°‘5 
Cent.),  on  being  placed  in  the  same  strong  solution, 
did  not  undergo  aggregation,  the  cells  becoming  filled 
with  brownish,  pulpy,  or  muddy  matter.  / With  leaves 
subjected  to  temperatures  between  these  two  extremes 
of  120°  and  150°  Fahr.  (48°*8  and  65°*5  Cent.),  there 
were  gradations  in  the  completeness  of  the  process ; 
the  former  temperature  not  preventing  aggregation 
from  the  subsequent  action  of  carbonate  of  ammonia, 
the  latter  quite  stopping  it.  /Thus,  leaves  immersed 
in  water,  heated  to  130°  (54°'4  Cent.),  and  then  in  the 
solution,  formed  perfectly  defined  spheres,  but  these 
were  decidedly  smaller  than  in  ordinary  cases.  With 
other  leaves  heated  to  140°  (60°  Cent.),  the  spheres 
were  extremely  small,  yet  well  defined,  but  many  of 
the  cells  contained,  in  addition,  some  brownish  pulpy 
matter.  In  two  cases  of  leaves  heated  to  145°  (62°*7 
Cent.),  a few  tentacles  could  be  found  with  some  of 
their  cells  containing  a few  minute  spheres;  whilst 
the  other  cells  and  other  whole  tentacles  included 
only  the  brownish,  disintegrated  or  pulpy  matter.  ^ 

I The  fluid  within  the  cells  of  the  tentacles  must  be 
in  an  oxygenated  condition,  in  order  that  the  force  or 


Chap.  III.  THE  PKOCESS  OF  AGGKEGATIOK.  59 

influence  which  induces  aggregation  should  be  trans- 
mitted at  the  proper  rate  from  cell  to  cell/  A plant, 
with  its  roots  in  water,  was  left  for  45  m.  in  a vessel 
containing  122  oz.  of  carbonic  acid.  A leaf  from  this 
plant,  and,  for  comparison,  one  from  a fresh  plant,  were 
both  immersed  for  1 hr.  in  a rather  strong  solution 
of  carbonate  of  ammonia.  They  were  then  compared, 
and  certainly  there  was  much  less  aggregation  in  the 
leaf  which  had  been  subjected  to  the  carbonic  acid 
than  in  the  other.  Another  plant  was  exposed  in 
the  same  vessel  for  2 hrs.  to  carbonic  acid,  and  one  of 
its  leaves  was  then  placed  in  a solution  of  one  part  of 
the  carbonate  to  437  of  water;  the  glands  were  in- 
stantly blackened,  showing  that  they  had  absorbed, 
and  that  their  contents  were  aggregated;  but  in  the 
cells  close  beneath  the  glands  there  w^as  no  aggre- 
gation even  after  an  interval  of  3 hrs.  After  4 hrs. 
15  m.  a few  minute  spheres  of  protoplasm  were  formed 
in  the^e  cells,  but  even  after  5 hrs.  30  m.  the  aggre- 
gation did  not  extend  down  the  pedicels  for  a length 
equal  to  that  of  the  glands.  After  numberless  trials 
with  fresh  leaves  immersed  in  a solution  of  this 
strength,  I have  never  seen  the  aggregating  action 
transmitted  at  nearly  so  slow  a rate.  'Another  plant 
was  left  for  2 hrs.  in  carbonic  acid,  but  was  then 
exposed  for  20  m.  to  the  open  air,  during  which  time 
the  leaves,  being  of  a red  colour,  would  have  absorbed 
some  oxygen.  One  of  them,  as  well  as  a fresh  leaf 
for  comparison,  were  now  immersed  in  the  same  solu- 
tion as  before.  The  former  were  looked  at  repeatedly, 
and  after  an  interval  of  65  m.  a few  spheres  of 
protoplasm  were  first  observed  in  the  cells  close  be- 
neath the  glands,  but  only  in  two  or  three  of  the 
longer  tentacles.  ^ After  3 hrs.  the  aggregation  had 
travelled  down  the  pedicels  of  a few  of  the  tentacles 


60 


DROSERA  ROTUNDIFOLIA. 


Chap.  III. 


for  a length  equal  to  that  of  the  glands.  On  the  other 
hand,  in  the  fresh  leaf  similarly  treated,  aggregation 
was  plain  in  many  of  the  tentacles  after  15m.;  after 
65  m.  it  had  extended  down  the  pedicels  for  four,  five, 
or  more  times  the  lengths  of  the  glands;  and  after 
3 hrs.  the  cells  of  all  the  tentacles  were  affected  for 
one-third  or  one-half  of  their  entire  lengths.  [ Hence 
there  can  be  no  doubt  that  the  exposure  of  leaves  to 
carbonic  acid  either  stops  for  a time  the  process  of 
aggregation,  or  checks  the  transmission  of  the  proper 
influence  when  the  glands  are  subsequently  excited 
by  carbonate  of  ammonia;  and  this  substance  acts 
more  promptly  and  energetically  than  any  other.  It 
is  known  that  the  protoplasm  of  plants  exhibits  its 
spontaneous  movements  only  as  long  as  it  is  in  an 
oxygenated  condition;  and  so  it  is  with  the  white 
corpuscles  of  the  blood,  only  as  long  as  they  receive 
oxygen  from  the  red  corpuscles  f but  the  cases  above 
given  are  somewhat  different,  as  they  relate  to  the 
delay  in  the  generation  or  aggregation  of  the  masses 
of  protoplasm  by  the  exclusion  of  oxygen.f 

Summary  and  Concluding  RemarT^s.—The  process  of 
aggregation  is  independent  of  the  inflection  of  the 
tentacles  and  of  increased  secretion  from  the  glands. 
It  commences  within  the  glands,  whether  these  have 
been  directly  excited,  or  indirectly  by  a stimulus 
received  from  other  glands.  In  both  cases  the  pro- 
cess is  transmitted  from  cell  to  cell  down  the  whole 
length  of  the  tentacles,  being  arrested  for  a short 
time  at  each  transverse  partition.  With  pale-coloured 
leaves  the  first  change  which  is  perceptible,  but  only 


* With  respect  to  plants,  Sachs,  ‘ Quarterly  Journal  of  Micro* 
' Traite  de  Bot.,’  3rd  edit.,  1874,  scopical  Science,'  April  1874,  pi 
p.  864.  On  blood  corpuscles,  see  185.* 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 


61 


under  a high  power,  is  the  appearance  of  the  finest 
granules  in  the  fluid  within  the  cells,  making  it 
slightly  cloudy.  These  granules  soon  aggregate  into 
small  globular  masses.  ^ I have  seen  a cloud  of  this 
kind  appear  in  10  s.  after  a drop  of  a solution  of  car- 
bonate of  ammonia  had  been  given  to  a gland.  With 
dark  red  leaves  the  first  visible  change  often  is  the 
conversion  of  the  outer  layer  of  the  fluid  within  the 
cells  into  bag-like  masses.  The  aggregated  masses, 
however  they  may  have  been  developed,  incessantly 
change  their  forms  and  positions.  They  are  not  filled 
with  fluid,  but  are  solid  to  their  centres.  Ultimately 
the  colourless  granules  in  the  protoplasm  which  flows 
round  the  walls  coalesce  with  the  central  spheres  or 
masses ; but  there  is  still  a current  of  limpid  fluid 
flowing  within  the  cells.  As  soon  as  the  tentacles 
fully  re-expand,  the  aggregated  masses  are  redis- 
solved, and  the  cells  become  filled  with  homogeneous 
purple  fluid,  as  they  were  at  first.  The  process  of  re- 
dissolution  commences  at  the  bases  of  the  tentacles, 
thence  proceeding  upwards  to  the  glands ; and,  there- 
fore, in  a reversed  direction  to  that  of  aggregation. 

' Aggregation  is  excited  by  the  most  diversified 
causes, — by  the  glands  being  several  times  touched, — 
by  the  pressure  of  particles  of  any  kind,  and  as  these 
are  supported  by  the  dense  secretion,  they  can  hardly 
press  on  the  glands  with  the  weight  of  a millionth  of 
a grain, — by  the  tentacles  being  cut  off  close  beneath 


* According  to  Hofmeister  (as 
quoted  by  Sachs,  ‘ Traite  de  Hot.’ 
1874,  p.  958),  very  slight  pres- 
sure on  the  cell-membrane  arrests 
immediately  the  movements  of 
the  protoplasm,  and  even  deter- 
mines its  separation  from  the 
walls.  But  the  process  of  aggre- 


gation is  a different  phenomenon, 
as  it  relates  to  the  contents  of  the 
cells,  and  only  secondarily  to  the 
layer  of  protoplasm  which  flows 
along  the  w^alls ; though  no  doubt 
the  effects  of  pressure  or  of  a 
touch  on  the  outside  must  be 
transmitted  through  this  layer. 


62 


DROSERA  ROTUNDIFOLIA. 


Chap.  III. 


the  glands, — by  the  glands  absorbing  yarious  fluids  or 
matter  dissolved  out  of  certain  bodies, — by  exosmose, — 
and  by  a certain  degree  of  heat,  i On  the  other  hand, 
a temperature  of  about  150"^  Fahr.  (65°‘5  Cent.)  does 
not  excite  aggregation ; nor  does  the  sudden  crushing 
of  a gland.  If  a cell  is  ruptured,  neither  the  exuded 
matter  nor  that  which  still  remains  within  the  cell 
undergoes  aggregation  when  carbonate  of  ammonia  is 
added.  A very  strong  solution  of  this  salt  and  rather 
large  bits  of  raw  meat  prevent  the  aggregated  masses 
being  well  developed.  From  these  facts  we  may  con- 
clude that  the  protoplasmic  fluid  within  a cell  does 
not  become  aggregated  unless  it  be  in  a living  state, 
and  only  imperfectly  if  the  cell  has  been  injured.  We 
have  also  seen  that  the  fluid  must  be  in  an  oxygen- 
ated state,  in  order  that  the  process  of  aggregation 
should  travel  from  cell  to  cell  at  the  proper  rate. 

Various  nitrogenous  organic  fluids  and  salts  of  am- 
monia induce  aggregation,  ^but  in  different  degrees 
and  at  very  different  rates.  ^Carbonate  of  ammonia  is 
the  most  powerful  of  all  known  substances;  the  ab- 
sorption of  tt^Vo-o  of  a grain  (*000482  mg.)  by  a gland 
suffices  to  cause  all  the  cells  of  the  same  tentacle  to 
become  aggregated.  ^ The  first  effect  of  the  carbonate 
and  of  certain  other  salts  of  ammonia,  as  well  as  of 
some  other  fluids,  is  the  darkening  or  blackening  of 
the  glands.  This  follows  even  from  long  immersion 
in  cold  distilled  water.  It  apparently  depends  in 
chief  part  on  the  strong  aggregation  of  their  cell- 
contents,  which  thus  become  opaque,  and  do  not 
reflect  light.  Some  other  fluids  render  the  glands  of 
a brighter  red;  whilst  certain  acids,  though  much 
diluted,  the  poison  of  the  cobra-snake,  &c.,  make  the 
glands  perfectly  white  and  opaque ; and  this  seems  to 
depend  on  the  coagulation  of  their  contents  without 


Chap.  III.  THE  PROCESS  OF  AGGREGATION. 


63 


any  aggregation.  Nevertheless,  before  being  thus 
affected,  they  are  able,  at  least  in  some  cases,  to  excite 
aggregation  in  their  own  tentacles. 

That  the  central  glands,  if  irritated,  send  centri- 
fugally  some  influence  to  the  exterior  glands,  causing 
them  to  send  back  a centripetal  influence  inducing 
aggregation,  is  perhaps  the  most  interesting  fact  given 
in  this  chapter.  But  the  whole  process  of  aggrega- 
tion is  in  itself  a striking  phenomenon.  Whenever 
the  peripheral  extremity  of  a nerve  is  touched  or 
pressed,  and  a sensation  is  felt,  it  is  believed  that  an 
invisible  molecular  change  is  sent  from  one  end  of  the 
nerve  to  the  other;  but  when  a gland  of  Drosera  is 
repeatedly  touched  or  gently  pressed,  we  can  actually 
see  a molecular  change  proceeding  from  the  gland 
down  the  tentacle ; though  this  change  is  probably  of 
a very  different  nature  from  that  in  a nerve.  Finally, 
as  so  many  and  such  widely  different  causes  excite 
aggregation,  it  would  appear  that  the  living  matter 
within  the  gland-cells  is  in  so  unstable  a condition 
that  almost  any  disturbance  suffices  to  change  its 
molecular  nature,  as  in  the  case  of  certain  chemical 
compounds.  * And  this  change  in  the  glands,  whether 
excited  directly,  or  indirectly  by  a stimulus  received 
from  other  glands,  is  transmitted  from  cell  to  cell, 
causing  granules  of  protoplasm  either  to  be  actually 
generated  in  the'  previously  limpid  fluid  or  to  coalesce 
and  thus  to  become  visible. 

Supplementary  Observations  on  the  Process  of  Aggre- 
gation in  the  Boots  of  Plants. 

It  will  hereafter  be  seen  that  a weak  solution  of  the  car- 
bonate of  ammonia  induces  aggregation  in  the  cells  of  the  roots 
of  Drosera ; and  this  led  me  to  make  a few  trials  on  the  roots 
|of  other  plants.  I dug  up  in  the  latter  part  of  October  the 
first  weed  which  1 met  with,  viz.  Euphorhia  peplus,  being  care- 


61 


DKOSEKA  KOTUNDIFOLIA. 


Chaf.  III. 


ful  not  to  injure  the  roots ; these  were  washed  and  placed  in  a 
little  solution  of  one  part  of  carbonate  of  ammonia  to  146  of 
water.  In  less  than  one  minute  I saw  a cloud  travelling  from 
cell  to  cell  up  the  roots,  with  wonderful  rapidity.  After  from 
8 m.  to  9 m.  the  fine  granules,  which  caused  this  cloudy  appear- 
ance, became  aggregated  towards  the  extremities  of  the  roots 
into  quadrangular  masses  of  brown  matter ; and  some  of  these 
soon  changed  their  forms  and  became  spherical.  Some  of  the 
cells,  however,  remained  unaffected.  I repeated  the  experi- 
ment with  another  plant  of  the  same  species,  but  before  I could 
get  the  specimen  into  focus  under  the  microscope,  clouds  of 
granules  and  quadrangular  masses  of  reddish  and  brown 
matter  were  formed,  and  had  run  far  up  all  the  roots.  A fresh 
root  was  now  left  for  18  hrs.  in  a drachm  of  a solution  of  one 
part  of  the  carbonate  to  437  of  water,  so  that  it  received  | of 
a grain,  or  2*024  mg.  When  examined,  the  cells  of  all  the 
roots  throughout  their  whole  length  contained  aggregated 
masses  of  reddish  and  brown  matter.  Before  making  these 
experiments,  several  roots  were  closely  examined,  and  not  a 
trace  of  the  cloudy  appearance  or  of  the  granular  masses  could 
be  seen  in  any  of  them.  Boots  were  also  immersed  for  35  m. 
in  a solution  of  one  part  of  carbonate  of  potash  to  218  of  water  j 
but  this  salt  produced  no  effect. 

I may  here  add  that  thin  slices  of  the  stem  of  the  Euphorbia 
were  placed  in  the  same  solution,  and  the  cells  which  were 
green  instantly  became  cloudy,  whilst  others  which  were  before 
colourless  were  clouded  with  brown,  owing  to  the  formation  of 
numerous  granules  of  this  tint.  I have  also  seen  with  various 
kinds  of  leaves,  left  for  some  time  in  a solution  of  carbonate  of 
ammonia,  that  the  grains  of  chlorophyll  ran  together  and 
partially  coalesced;  and  this  seems  to  be  a form  of  aggregation. 

Plants  of  duck-weed  (Lemna)  were  left  for  between  30  m.  and 
45  m.  in  a solution  of  one  part  of  this  same  salt  to  146  of  water, 
and  three  of  their  roots  were  then  examined.  In  two  of  them, 
all  the  cells  which  had  previously  contained  only  limpid  fluid 
now  included  little  green  spheres.  After  from  1^  hr.  to  2 hrs. 
similar  spheres  appeared  in  the  cells  on  the  borders  of  the 
leaves ; but  whether  the  ammonia  had  travelled  up  the  roots  or 
had  been  directly  absorbed  by  the  leaves,  I cannot  say.  As  one 
species,  L^Tnincb  avvliizd,  produces  no  roots,  the  latter  alternative 
is  perhaps  the  most  probable.  After  about  2^  hrs.  some  of  the 
little  green  spheres  in  the  roots  were  broken  up  into  small 
granules  which  exhibited  Brownian  movements.  Some  duck- 
weed was  also  left  for  1 hr.  30  m.  in  a solution  of  one  part  of 


CHAP.m.  the  pkocess  of  aggkegation. 


65 


carbonate  of  potash  to  218  of  water,  and  no  decided  change 
conld  be  perceived  in  the  cells  of  the  roots;  but  when  these 
same  roots  were  placed  for  25  m.  in  a solution  of  carbonate  of 
ammonia  of  the  same  strength,  little  green  spheres  were  formed. 

A green  marine  alga  was  left  for  some  time  in  this  same  solu- 
tion, but  was  very  doubtfully  affected.  On  the  other  hand,  a 
red  marine  alga,  with  finely  pinnated  fronds,  was  strongly 
affected.  The  contents  of  the  cells  aggregated  themselves  into 
broken  rings,  still  of  a red  colour,  which  very  slowly  and 
slightly  changed  their  shapes,  and  the  central  spaces  within 
these  rings  became  cloudy  with  red  granular  matter.  The 
facts  here  given  (whether  they  are  new,  I know  not)  indicate 
that  interesting  results  would  perhaps  be  gained  by  observing 
the  action  of  various  saline  solutions  and  other  fluids  on  the 
roots  of  plants. 


66 


DEOSERA  EOTUNDIFOLIA. 


Chap  IV. 


CHAPTEE  IV. 

The  Effects  of  Heat  on  the  Leaves. 

Nature  of  the  experiments  — Effects  of  boiling  water  — Warm  watei 
causes  rapid  inflection  — Water  at  a higher  temperature  does  not 
cause  immediate  inflection,  but  does  not  kill  the  leaves,  as  shown 
by  their  subsequent  re-expansion  and  by  the  aggregation  of  the 
protoplasm  — A still  higher  temperature  kills  the  leaves  and 
coagulates  the  albuminous  contents  of  the  glands. 

In  my  observations  on  Drosera  rotundifolia,  the  leaves 
seemed  to  be  more  quickly  inflected  over  animal  sub- 
stances, and  to  remain  inflected  for  a longer  period 
during  very  warm  than  during  cold  weather.  I 
wished,  therefore,  to  ascertain  whether  heat  alone 
would  induce  inflection,  and  what  temperature  was 
the  most  efficient.  Another  interesting  point  pre- 
sented itself,  namely,  at  what  degree  life  was  extin- 
guished ; for  Drosera  offers  unusual  facilities  in  this 
respect,  not  in  the  loss  of  the  power  of  inflection,  but 
in  that  of  subsequent  re-expansion,  and  more  espe- 
cially in  the  failure  of  the  protoplasm  to  become 
aggregated,  when  the  leaves  after  being  heated  are 
immersed  in  a solution  of  carbonate  of  ammonia.* 


* When  my  experiments  on  the 
effects  of  heat  were  made,  I was 
not  aware  that  the  subject  had 
been  carefully  investigated  by 
several  observers.  For  instance, 
Sachs  is  convinced  (‘  Traite  de 
Botanique/  1874,  pp.  772,  854) 
that  the  most  different  kinds  of 
plants  all  perish  if  kept  for  10  m. 
in  water  at  45°  to  46°  Cent.,  or 
113°  to  115°Fahr. ; and  he  con- 


cludes that  the  protoplasm  with- 
in their  cells  always  coagulates, 
if  in  a damp  condition,  at  a tem- 
perature of  between  50°  and  60° 
Cent.,  or  122°  to  140°  Fahr.  Max 
Schultze  and  Kiihne  (as  quoted 
by  Dr.  Bastian  in  ‘ Contemp. 
Review,’  1874,  p.  528)  “ found 
that  the  protoplasm  of  plant- 
cells,  with  which  they  experi- 
mented, was  always  killed  an(? 


Ciup.  IV. 


THE  EFFECTS  OF  HEAT. 


67 


My  experiments  were  tried  in  the  following  manner.  Leaves 
were  cut  off,  and  this  does  not  in  the  least  interfere  with  their 
powers;  for  instance,  three  cut-off  leaves,  with  bits  of  meat 
placed  on  them,  were  kept  in  a damp  atmosphere,  and  after 
23  hrs.  closely  embraced  the  meat  both  with  their  ten- 
tacles and  blades ; and  the  protoplasm  within  their  cells  was 
well  aggregated.  Three  ounces  of  doubly  distilled  water  was 
heated  in  a porcelain  vessel,  with  a delicate  thermometer 
having  a long  bulb  obliquely  suspended  in  it.  The  water  was 
gradually  raised  to  the  required  temperature  by  a spirit-lamp 
moved  about  under  the  vessel;  and  in  all  cases  the  leaves 
were  continually  waved  for  some  minutes  close  to  the  bulb. 
They  were  then  placed  in  cold  water,  or  in  a solution  of  car- 
bonate of  ammonia.  In  other  cases  they  were  left  in  the  water, 
which  had  been  raised  to  a certain  temperature,  until  it  cooled. 
Again  in  other  cases  the  leaves  were  suddenly  plunged  into 
water  of  a certain  temperature,  and  kept  there  for  a specified 
time.  Considering  that  the  tentacles  are  extremely  delicate, 
and  that  their  coats  are  very  thin,  it  seems  scarcely  possible 
that  the  fluid  contents  of  their  cells  should  not  have  been 
heated  to  within  a degree  or  two  of  the  temperature  of  the 
surrounding  water.  Any  further  precautions  would,  I think, 
have  been  superfluous,  as  the  leaves  from  age  or  constitutional 
causes  differ  slightly  in  their  sensitiveness  to  heat. 

It  will  be  convenient  first  briefly  to  describe  the  effects  of 
immersion  for  thirty  seconds  in  boiling  water.  The  leaves  are 
rendered  flaccid,  with  their  tentacles  bowed  backwards,  which, 
as  we  shall  see  in  a future  chapter,  is  probably  due  to  their 
outer  surfaces  retaining  their  elasticity  for  a longer  period  than 
their  inner  surfaces  retain  the  power  of  contraction.  The 
purple  fluid  within  the  cells  of  the  pedicels  is  rendered  finely 
granular,  but  there  is  no  true  aggregation ; nor  does  this  follow 


altered  by  a very  brief  expo- 
sure to  a temperature  of  118^° 
Fahr.  as  a maximum.’*  As  my 
results  are  deduced  from  special 
phenomena,  namely,  the  subse- 
quent aggregation  of  the  proto- 
plasm and  the  re-expansion  of 
the  tentacles,  they  seem  to  me 
worth  giving.  We  shall  find  that 
Hrosera  resists  heat  somewhat 
better  than  most  other  plants. 
That  there  should  be  consider- 


able differences  in  this  respect  is 
not  surprising,  considering  that 
some  low  vegetable  organisms 
grow  in  hot  springs  — cases  of 
which  have  been  collected  by 
Prof.  Wyman  (‘  American  Journal 
of  Science,’  vol.  xliv.  1867).  Thus, 
Dr.  Hooker  found  Confervas  in 
water  at  168°  Fahr. ; Humboldt, 
at  185°  Fahr. ; and  Descloizeaux, 
at  208°  Fahr. 


68 


DROSERA  ROTUNDIFOLIA. 


Chap  IV. 


when  the  leaves  are  subsequently  placed  in  a solution  of  car- 
bonate of  ammonia.  But  the  most  remarkable  change  is  that 
the  glands  become  opaque  and  uniformly  white ; and  this  may 
be  attributed  to  the  coagulation  of  their  albuminous  contents. 

My  first  and  preliminary  experiment  consisted  in  putting 
seven  leaves  in  the  same  vessel  of  water,  and  warming  it  slowly 
up  to  the  temperature  of  110°  Fahr.  (43°*3  Cent.) ; a leaf  being 
taken  out  as  soon  as  the  temperature  rose  to  80°  (26°*6  Cent.), 
another  at  85°,  another  at  90°,  and  so  on.  Each  leaf,  when  taken 
out,  was  placed  in  water  at  the  temperature  of  my  room,  and 
the  tentacles  of  all  soon  became  slightly,  though  irregularly, 
inflected.  They  were  now  removed  from  the  cold  water  and 
kept  in  damp  air,  with  bits  of  meat  placed  on  their  discs. 
The  leaf  which  had  been  exposed  to  the  temperature  of  110° 
became  in  15  m.  greatly  inflected;  and  in  2 hrs.  every  single 
tentacle  closely  embraced  the  meat.  So  it  was,  but  after  rather 
longer  intervals,  with  the  six  other  leaves.  It  appears,  there- 
fore, that  the  warm  bath  had  increased  their  sensitiveness 
when  excited  by  meat. 

I next  observed  the  degree  of  inflection  which  leaves  under- 
went within  stated  periods,  whilst  still  immersed  in  warm 
water,  kept  as  nearly  as  possible  at  the  same  temperature ; but 
I will  here  and  elsewhere  give  only  a few  of  the  many  trials 
made.  A leaf  was  left  for  10  m.  in  water  at  100°  (37°'7  Cent.), 
but  no  inflection  occurred.  A second  leaf,  however,  treated  in 
the  same  manner,  had  a few  of  its  exterior  tentacles  very 
slightly  inflected  in  6 m.,  and  several  irregularly  but  not  closely 
inflected  in  10  m.  A third  leaf,  kept  in  water  at  105°  to  106° 
(40°.5  to  41°T  Cent.),  was  very  moderately  inflected  in  6 m. 
A fourth  leaf,  in  water  at  110°  (43°‘3  Cent.),  was  somewhat  in- 
flected in  4 m.,  and  considerably  so  in  from  6 m,  to  7 m. 

Three  leaves  were  placed  in  water  which  was  heated  rather 
quickly,  and  by  the  time  the  temperature  rose  to  115° — 116° 
(46°T  to  46°*06  Ceht.),  all  three  were  inflected.  I then  removed 
the  lamp,  and  in  a few  minutes  every  single  tentacle  was 
closely  inflected.  The  protoplasm  within  the  cells  was  not 
killed,  for  it  was  seen  to  be  in  distinct  movement;  and  the 
leaves,  having  been  left  in  cold  water  for  20  hrs.,  re-expanded. 
Another  leaf  was  immersed  in  water  at  100°  (37°-7  Cent.),  which 
was  raised  to  120°  (48°*8  Cent.) ; and  all  the  tentacles,  except 
the  extreme  marginal  ones,  soon  became  closely  inflected. 
The  leaf  was  now  placed  in  cold  water,  and  in  7 hrs.  30  m.  it 
had  partly,  and  in  10  hrs.  fully,  re-expanded.  On  the  follow- 
ing morning  it  was  immersed  in  a weak  solution  of  carbonate  of 


Chap.  IV. 


THE  EFFECTS  OF  HEAT. 


69 


ammonia,  and  the  glands  quickly  became  black,  with  strongly 
marked  aggregation  in  the  tentacles,  showing  that  the  proto- 
plasm was  alive,  and  that  the  glands  had  not  lost  their  power  of 
absorption.  Another  leaf  was  placed  in  water  at  110°  (43°*3 
Cent.)  which  was  raised  to  120°  (48°*8  Cent.) ; and  every  ten- 
tacle, excepting  one,  was  quickly  and  closely  inflected.  This  leaf 
was  now  immersed  in  a few  drops  of  a strong  solution  of  car- 
bonate of  ammonia  (one  part  to  109  of  water) ; in  10  m.  all  the 
glands  became  intensely  black,  and  in  2 hrs.  the  protoplasm  in 
the  cells  of  the  pedicels  was  well  aggregated.  Another  leaf  was 
suddenly  plunged,  and  as  usual  waved  about,  in  water  at  120°, 
and  the  tentacles  became  inflected  in  from  2 m.  to  3 m.,  but 
only  so  as  to  stand  at  right  angles  to  the  disc.  The  leaf  was 
now  placed  in  the  same  solution  (viz.  one  part  of  carbonate  of 
ammonia  to  109  of  water,  or  4 grs.  to  1 oz.,  which  I will  for 
the  future  designate  as  the  strong  solution),  and  when  I looked 
at  it  again  after  the  interval  of  an  hour,  the  glands  were 
blackened,  and  there  was  well-marked  aggregation.  After  an 
additional  interval  of  4 hrs.  the  tentacles  had  become  much 
more  inflected.  It  deserves  notice  that  a solution  as  strong  as 
this  never  causes  inflection  in  ordinary  cases.  Lastly  a leaf 
was  suddenly  placed  in  water  at  125°  (51°*6  Cent.),  and  was 
left  in  it  until  the  water  cooled;  the  tentacles  were  rendered 
of  a bright  red  and  soon  became  inflected.  The  contents  of 
the  cells  underwent  some  degree  of  aggregation,  which  in 
the  course  of  three  hours  increased ; but  the  masses  of  proto- 
plasm did  not  become  spherical,  as  almost  always  occurs  with 
leaves  immersed  in  a solution  of  carbonate  of  ammonia. 

We  learn  from  these  cases  that  a temperature  of 
from  120"*  to  125°  (48°*8  to  51°*6  Cent.)  excites  the 
tentacles  into  quick  movement,  but  does  not  kill  the 
leaves,  as  shown  either  by  their  subsequent  re-expansion 
or  by  the  aggregation  of  the  protoplasm.  We  shall 
now  see  that  a temperature  of  130°  (54:°‘4  Cent.)  is  too 
high  to  cause  immediate  inflection,  yet  does  not  kill 
the  leaves. 

Experiment  1. — A leaf  was  plunged,  and  as  in  all  cases 
waved  about  -for  a few  minutes,  in  water  at  130°  (54°  *4  Cent.), 
but  there  was  no  trace  of  inflection;  it  was  then  placed  in  cold 
water,  and  after  an  interval  of  15  m.  very  slow  movement  was 


70 


DROSERA  ROTUNDIFOLIA. 


Chap.  IV. 


distinctly  seen  in  a small  mass  of  protoplasm  in  one  of  the  cells 
of  a tentacle.*  After  a few  hours  all  the  tentacles  and  the 
blade  became  inflected. 

Experiment  2. — Another  leaf  was  plunged  into  wafer  at  130® 
to  131®,  and  as  before  there  was  no  inflection.  After  being  kept 
in  cold  water  for  an  hour,  it  was  placed  in  the  strong  solution 
of  ammonia,  and  in  the  course  of  65  m.  the  tentacles  were  con- 
siderably inflected.  The  glands,  which  before  had  been  rendered 
of  a brighter  red,  were  now  blackened.  The  protoplasm  in  the 
cells  of  the  tentacles  was  distinctly  aggregated ; but  the  spheres 
were  much  smaller  than  those  usually  generated  in  unheated 
leaves  when  subjected  to  carbonate  of  ammonia.  After  an 
additional  2 hrs.  all  the  tentacles,  excepting  six  or  seven,  were 
closely  inflected. 

Experiment  3. — A similar  experiment  to  the  last,  with  exactly 
the  same  results. 

Experiment  4. — A fine  leaf  was  placed  in  water  at  100®  (37®  * 7 
Cent.),  which  was  then  raised  to  145®  (62°  *7  Cent.).  Soon  after 
immersion,  there  was,  as  might  have  been  expected,  strong 
inflection.  The  leaf  was  now  removed  and  left  in  cold  water ; 
but  from  having  been  exposed  to  so  high  a temperature,  it 
never  re-expanded. 

Experiment  5. — Leaf  immersed  at  130®  (54®*4  Cent.),  and  the 
water  raised  to  145®  (62®  *7  Cent.),  there  was  no  immediate  in- 
flection ; it  was  then  placed  in  cold  water,  and  after  1 hr.  20  m. 
some  of  the  tentacles  on  one  side  became  inflected.  This 
leaf  was  now  placed  in ' the  strong  solution,  and  in  40  m.  all 
the  submarginal  tentacles  were  well  inflected,  and  the  glands 
blackened.  After  an  additional  interval  of  2 hrs.  45  m.  all  the 
tentacles,  except  eight  or  ten,  were  closely  inflected,  with  their 
cells  exhibiting  a slight  degree  of  aggregation ; but  the  spheres 
of  protoplasm  were  very  small,  and  the  cells  of  the  exterior 
tentacles  contained  some  pulpy  or  disintegrated  brownish 
matter. 

Experiments  6 and  7. — Two  leaves  were  plunged  in  water  at 
135®  (57®  * 2 Cent.)  which  was  raised  to  145®  (62®  * 7 Cent.) ; neither 
became  inflected.  One  of  these,  however,  after  having  been  left 
for  31  m.  in  cold  water,  exhibited  some  slight  inflection,  which 
increased  after  an  additional  interval  of  1 hr.  45  m.,  until 


* Sachs  states  (‘  Traite  de  Bo-  after  they  >Yere  exposed  for  1 m. 
tanique,’  1874,  p.  855)  that  the  in  water  to  a temperature  of  47® 
movements  of  the  protoplasm  in  to  48®  Cent.,  Or  117®  to  119® 
the  hairs  of  a Cucurbita  ceased  Fahr. 


Chap.  IV, 


THE  EFFECTS  OF  HEAT. 


71 


all  the  tentacles,  except  sixteen  or  seventeen,  were  more  or  less 
inflected ; but  the  leaf  was  so  much  injured  that  it  never  re- 
expanded. The  other  leaf,  after  having  been  left  for  half  an 
hour  in  cold  water,  was  put  into  the  strong  solution,  but  no 
inflection  ensued;  the  glands,  however,  were  blackened,  and  in 
some  cells  there  was  a little  aggregation,  the  spheres  of  proto- 
plasm being  extremely  small;  in  other  cells,  especially  in  the 
exterior  tentacles,  there  was  much  greenish-brown  pulpy 
matter. 

Experiment  8. — A leaf  was  plunged  and  waved  about  for  a 
few  minutes  in  water  at  140°  (60°  Cent.),  and  was  then  left  for 
half  an  hour  in  cold  water,  but  there  was  no  inflection.  It  was 
now  placed  in  the  strong  solution,  and  after  2 hrs.  80  m.  the 
inner  submarginal  tentacles  were  well  inflected,  with  their 
glands  blackened,  and  some  imperfect  aggregation  in  the  cells 
of  the  pedicels.  Three  or  four  of  the  glands  were  spotted  with 
the  white  porcelain- like  structure,  like  that  produced  by  boiling 
water.  I have  seen  this  result  in  no  other  instance  after  an 
immersion  of  only  a few  minutes  in  water  at  so  low  a tempe- 
rature as  140°,  and  in  only  one  leaf  out  of  four,  after  a similar 
immersion  at  a temperature  of  145°  Fahr.  On  the  other  hand, 
with  two  leaves,  one  placed  in  water  at  145°  (62° ’7  Cent.),  and 
the  other  in  water  at  140°  (60°  Cent.),  both  being  left  therein 
until  the  water  cooled,  the  glands  of  both  became  white  and 
porcelain-like.  So  that  the  duration  of  the  immersion  is  an 
important  element  in  the  result. 

Experiment  9. — A leaf  was  placed  in  water  at  140°  (60°  Cent.), 
which  was  raised  to  150°  (65°  *5  Cent.) ; there  was  no  inflection ; 
on  the  contrary,  the  outer  tentacles  were  somewhat  bowed  back- 
wards. The  glands  became  like  porcelain,  but  some  of  them 
were  a little  mottled  with  purple.  The  bases  of  the  glands  were 
often  more  affected  than  their  summits.  This  leaf  having  been 
left  in  the  strong  solution  did  not  undergo  any  inflection  or 
aggregation. 

Experiment  10. — A leaf  was  plunged  in  water  at  150°  to  150i° 
(65°  * 5 Cent.) ; it  became  somewhat  flaccid,  with  the  outer  ten- 
tacles slightly  reflexed,  and  the  inner  ones  a little  bent  inwards, 
but  only  towards  their  tips ; and  this  latter  fact  shows  that  the 
movement  was  not  one  of  true  inflection,  as  the  basal  part 
alone  normally  bends.  The  tentacles  were  as  usual  rendered  of 
a very  bright  red,  with  the  glands  almost  white  like  porcelain, 
yet  tinged  with  pink.  The  leaf  having  been  placed  in  the 
strong  solution,  the  cell-contents  of  the  tentacles  became  of  a 
muddy  brown,  with  no  trace  of  aggregation. 


72 


DKOSERA  ROTUNDIFOLIA. 


Chap.  IY, 


Experiment  11. — A leaf  was  immersed  in  water  at  145°  (62°  *7 
Cent),  which  was  raised  to  156°  (68°  • 8 Cent.).  The  tentacles 
became  bright  red  and  somewhat  reflexed,  with  almost  all  the 
glands  like  porcelain;  those  on  the  disc  being  still  pinkish, 
those  near  the  margin  quite  white.  The  leaf  being  placed  as 
usual  first  in  cold  water  and  then  in  the  strong  solution,  the 
cells  in  the  tentacles  became  of  a muddy  greenish  brown,  with 
the  protoplasm  not  aggregated.  Nevertheless,  four  of  the  glands 
escaped  being  rendered  like  porcelain,  and  the  pedicels  of  these 
glands  were  spirally  curled,  like  a French  horn,  towards  their 
upper  ends;  but  this  can  by  no  means  be  considered  as  a 
case  of  true  inflection.  The  protoplasm  within  the  cells  of  the 
twisted  portions  was  aggregated  into  distinct  though  excessively 
minute  purple  spheres.  This  case  shows  clearly  that  the  proto- 
plasm, after  having  been  exposed  to  a high  temperature  for  a 
few  minutes,  is  capable  of  aggregation  when  afterwards  sub- 
jected to  the  action  of  carbonate  of  ammonia,  unless  the  heat 
has  been  sufficient  to  cause  coagulation. 

Concluding  BemarTcs. — As  the  hair-like  tentacles  are 
extremely  thin  and  have  delicate  walls,  and  as  the 
leaves  were  waved  about  for  some  minutes  close  to  the 
bulb  of  the  thermometer,  it  seems  scarcely  possible 
that  they  should  not  have  been  raised  very  nearly  to 
the  temperature  which  the  instrument  indicated. 
From  the  eleven  last  observations  we  see  that  a tem- 
perature of  130^^  Cent.)  never  causes  the  imme- 

diate inflection  of  the  tentacles,  though  a temperature 
from  120°  to  125°  (48°*8  to  51°*6  Cent.)  quickly  pro- 
duces this  effect.  But  the  leaves  are  paralysed  only 
for  a time  by  a temperature  of  130°,  as  afterwards, 
whether  left  in  simple  water  or  in  a solution  of  car- 
bonate of  ammonia,  they  become  inflected  and  their 
protoplasm  undergoes  aggregation,  i This  great  dif- 
ference in  the  eflects  of  a higher  and  lower  tempera- 
ture may  be  compared  with  that  from  immersion  in 
strong  and  weak  solutions  of  the  salts  of  ammonia  ; for 
the  former  do  not  excite  movement,  whereas  the  latter 
act  energetically.  A temporary  suspension  of  the 


Chap.  IV, 


THE  EFFECTS  OF  HEAT. 


73 


power  of  movement  due  to  heat  is  called  by  Sachs'^ 
heat-rigidity ; and  this  in  the  case  of  the  sensitive- 
plant  (Mimosa)  is  induced  by  its  exposure  for  a few 
minutes  to  humid  air,  raised  to  120° — 122°  Fahr.,  or 
49°  to  50°  Cent.  \ It  deserves  notice  that  the  leaves  of 
Drosera,  after  being  immersed  in  water  at  130°  Fahr., 
are  excited  into  movement  by  a solution  of  the  car- 
bonate so  strong  that  it  would  paralyse  ordinary 
leaves  and  cause  no  inflection.  \ 

The  exposure  of  the  leaves  for  a few  minutes  even 
to  a temperature  of  145°  Fahr.  (62°*7  Cent.)  does  not 
always  kill  them ; as  when  afterwards  left  in  cold 
water,  or  in  a strong  solution  of  carbonate  of  ammo- 
nia, they  generally,  though  not  always,  become  in- 
flected ; and  the  protoplasm  within  their  cells  under- 
goes aggregation,  though  the  spheres  thus  formed  are 
extremely  small,  with  many  of  the  cells  partly  filled 
with  brownish  muddy  matter.  In  two  instances,  when 
leaves  were  immersed  in  water,  at  a lower  temperature 
than  130°  (54°*4  Cent.),  which  was  then  raised  to  145° 
(62°’7  Cent.),  they  became  during  the  earlier  period 
of  immersion  inflected,  but  on  being  afterwards  left 
in  cold  water  were  incapable  of  re-expansion.  Ex- 
posure for  a few  minutes  to  a temperature  of  145° 
sometimes  causes  some  few  of  the  more  sensitive 
glands  to  be  speckled  with  the  porcelain-like  appear- 
ance ; and  on  one  occasion  this  occurred  at  a tempera- 
ture of  140°  (60°  Cent.).  On  another  occasion,  when 
a leaf  was  placed  in  water  at  this  temperature  of  only 
140°,  and  left  therein  till  the  water  cooled,  every 
gland  became  like  porcelain.  Exposure  for  a few 
minutes  to  a temperature  of  150°  (65°*5  Cent.)  gene- 
rally produces  this  effect,  yet  many  glands  retain  a 


"•  ‘ Traite  de  Hot.*  1874,  p.  1034. 


74 


DKOSERA  EOTUNDIFOLIA. 


Chap.  IV. 


pinkish  colour,  and  many  present  a speckled  appear- 
ance. This  high  temperature  never  causes  true  inflec- 
tion ; on  the  contrary,  the  tentacles  commonly  become 
reflexed,  though  to  a less  degree  than  when  immersed 
in  boiling  water ; and  this  apparently  is  due  to  their 
passive  power  of  elasticity.  After  exposure  to  a tem- 
perature of  150"^  Fahr.,  the  protoplasm,  if  subsequently 
subjected  to  carbonate  of  ammonia,  instead  of  under- 
going aggregation,  is  converted  into  disintegrated  or 
pulpy  discoloured  matter.  In  short,  the  leaves  are 
generally  killed  by  this  degree  of  heat ; but  owing  to 
differences  of  age  or  constitution,  they  vary  somewhat 
in  this  respect.  In  one  anomalous  case,  four  out  of 
the  many  glands  on  a leaf,  which  had  been  immersed 
in  water  raised  to  156°  (68°’8  Cent.),  escaped  being 
rendered  porcellanous ; * and  the  protoplasm  in  the 
cells  close  beneath  these  glands  underwent  some 
slight,  though  imperfect,  degree  of  aggregation. 

Finally,  it  is  a remarkable  fact  that  the  leaves  of 
Drosera  rotundifolia,  which  flourishes  on  bleak  upland 
moors  throughout  Great  Britain,  and  exists  (Hooker) 
within  the  Arctic  Circle,  should  be  able  to  withstand 
for  even  a short  time  immersion  in  water  heated  to  a 
temperature  of  145°.t 

It  may  be  worth  adding  that  immersion  in  cold 


* As  the  opacity  and  porcelain- 
like  appearance  of  the  glands  is 
probably  due  to  the  coagulation 
of  the  albumen,  I may  add,  on  the 
authority  of  Dr.  Burdon  Sander- 
son, that  albumen  coagulates  at 
about  155°,  but,  in  presence  of 
acids,  the  temperature  of  coagula- 
tion is  lower.  The  leaves  of  Dro- 
sera contain  an  acid,  and  perhaps 
a difference  in  the  amount  con- 
tained may  account  for  the  slight 


differences  in  the  results  above 
recorded. 

t It  appears  that  cold-blooded 
animals  are,  as  might  have  been 
expected,  far  more  sensitive  to  an 
increase  of  temperature  than  is 
Drosera.  Thus,  as  I hear  from  Dr. 
Burdon  Sanderson,  a frog  begins 
to  be  distressed  in  water  at  a tem- 
perature of  only  85°  Fahr.  At  95° 
the  muscles  become  rigid,  and  the 
animal  dies  in  a stiffened  condition 


Chap.  IV. 


THE  EFFECTS  OF  HEAT. 


75 


water  does  not  cause  any  inflection : I suddenly  placed 
four  leaves,  taken  from  plants  which  had  been  kept  for 
several  days  at  a high  temperature,  generally  about 
75°  Fahr.  (23°*8  Cent.),  in  water  at  45°  (7°*2  Cent.),  but 
they  were  hardly  at  all  affected ; not  so  much  as  some 
other  leaves  from  the  same  plants,  which  were  at  the 
same  time  immersed  in  water  at  75° ; for  these  became 
in  a slight  degree  inflected. 


76 


DROSERA  ROTUNDIFOLIA. 


Chap.  V, 


CHAPTER  V. 

The  Effects  of  Non-nitrogenous  and  Nitrogenous  Organic  Fluids 
ON  THE  Leaves. 

Non-nitrogenous  fluids — Solutions  of  gum  arabic  — Sugar  — Starch 
— Diluted  alcohol  — Olive  oil  — Infusion  and  decoction  of  tea  — 
Nitrogenous  fluids  — Milk  — Urine  — Liquid  albumen  — Infusion 
of  raw  meat  — Impure  mucus  — Saliva  — Solution  of  isinglass  — 
Difference  in  the  action  of  these  two  sets  of  fluids  — Decoction  of 
green  peas  — Decoction  and  infusion  of  cabbage  — Decoction  of 
grass  leaves. 

When,  in  1860, 1 first  observed  Drosera,  and  was  led  to 
believe  that  the  leaves  absorbed  nutritious  matter  from 
the  insects  which  they  captured,  it  seemed  to  me  a 
good  plan  to  make  some  preliminary  trials  with  a few 
common  fluids,  containing  and  not  containing  nitro- 
genous matter ; and  the  results  are  worth  giving. 

In  all  the  following  cases  a drop  was  allowed  to  fall 
from  the  same  pointed  instrument  on  the  centre  of  the 
leaf;  and  by  repeated  trials  one  of  these  drops  was 
ascertained  to  be  on  an  average  very  nearly  half  a 
minim,  or  of  a fluid  ounce,  or  ’0295  ml.  But  these 
measurements  obviously  do  not  pretend  to  any  strict 
accuracy ; moreover,  the  drops  of  the  viscid  fluids  were 
plainly  larger  than  those  of  water.  Only  one  leaf  on 
the  same  plant  was  tried,  and  the  plants  were  col- 
lected from  two  distant  localities.  The  experiments 
were  made  during  August  and  September.  In  judging 
of  the  effects,  one  caution  is  necessary:  if  a drop  of 
any  adhesive  fluid  is  placed  on  an  old  or  feeble  leaf, 
the  glands  of  which  have  ceased  to  secrete  copiously, 
the  drop  sometimes  dries  up,  especially  if  the  plant 


Chap.  V. 


EFFECTS  OF  ORGANIC  FLUIDS. 


77 


is  kept  in  a room,  and  some  of  the  central  and  sub- 
marginal tentacles  are  thus  drawn  together,  giving  to 
them  the  false  appearance  of  having  become  inflected. 
This  sometimes  occurs  with  water,  as  it  is  rendered 
adhesive  by  mingling  with  the  viscid  secretion. 
Hence  the  only  safe  criterion,  and  to  this  alone  I 
have  trusted,  is  the  bending  inwards  of  the  exterior 
tentacles,  which  have  not  been  touched  by  the  fluid,  or 
at  most  only  at  their  bases,  fin  this  case  the  move- 
ment is  wholly  due  to  the  central  glands  having  been 
stimulated  by  the  fluid,  and  transmitting  a motor 
impulse  to  the  exterior  tentacles.  The  blade  of  the 
leaf  likewise  often  curves  inwards,  in  the  same  manner 
as  when  an  insect  or  bit  of  meat  is  placed  on  the 
disc.  This  latter  movement  is  never  caused,  as  far 
as  I have  seen,  by  the  mere  drying  up  of  an  ad- 
hesive fluid  and  the  consequent  drawing  together  of 
the  tentacles.  ^ 

First  for  the  non-nitrogenous  fluids.  As  a pre- 
liminary trial,  drops  of  distilled  water  were  placed  on 
between  thirty  and  forty  leaves,  and  no  effect  whatever 
was  produced;  nevertheless,  in  some  other  and  rare 
cases,  a few  tentacles  became  for  a short  time  in- 
flected; but  this  may  have  been  caused  by  the 
glands  having  been  accidentally  touched  in  getting 
the  leaves  into  a proper  position.  That  water  should 
produce  no  effect  might  have  been  anticipated,  as 
otherwise  the  leaves  would  have  been  excited  into 
movement  by  every  shower  of  rain. 

Gum  am&ic.— -Solutions  of  four  degrees  of  strength  were  made ; 
one  of  six  grains  to  the  ounce  of  water  (one  part  to  73) ; a second 
rather  stronger,  yet  very  thin  ; a third  moderately  thick,  and  a 
fourth  so  thick  that  it  would  only  just  drop  from  a pointed 
instrument.  These  were  tried  on  fourteen  leaves;  the  drops 
being  left  on  the  discs  from  24  hrs.  to  44  hrs. ; generally  about 


78 


DROSERA  ROTUNDIFOLIA. 


Chap.  V. 


30  hrs.  Inflection  was  never  thus  caused.  It  is  necessary 
to  try  pure  gum  arabic,  for  a friend  tried  a solution  bought 
ready  prepared,  and  this  caused  the  tentacles  to  bend ; but  he 
afterwards  ascertained  that  it  contained  much  animal  matter, 
probably  glue. 

Sugar, — Drops  of  a solution  of  white  sugar  of  three  strengths 
(the  weakest  containing  one  part  of  sugar  to  73  of  water)  were 
left  on  fourteen  leaves  from  32  hrs.  to  48  hrs. ; but  no  effect  was 
produced. 

Starch, — A mixture  about  as  thick  as  cream  was  dropped  on 
six  leaves  and  left  on  them  for  30  hrs.,  no  effect  being  produced. 
I am  surprised  at  this  fact,  as  I believe  that  the  starch  of  com- 
merce generally  contains  a trace  of  gluten,  and  this  nitrogenous 
substance  causes  inflection,  as  we  shall  see  in  the  next  chapter. 

Alcohol^  Diluted, — One  part  of  alcohol  was  added  to  seven  of 
water,  and  the  usual  drops  were  placed  on  the  discs  of  three 
leaves.  No  inflection  ensued  in  the  course  of  48  hrs.  To  ascer- 
tain whether  these  leaves  had  been  at  all  injured,  bits  of  meat 
were  placed  on  them,  and  after  24  hrs.  they  were  closely  inflected. 
I also  put  drops  of  sherry -wine  on  three  other  leaves ; no  inflec- 
tion was  caused,  though  two  of  them  seemed  somewhat  injured. 
We  shall  hereafter  see  that  cut-off  leaves  immersed  in  diluted 
alcohol  of  the  above  strength  do  not  become  inflected. 

Olive  Oil, — Drops  were  placed  on  the  discs  of  eleven  leaves,  and 
no  effect  was  produced  in  from  24  hrs.  to  48  hrs.  Four  of  these 
leaves  were  then  tested  by  bits  of  meat  on  their  discs,  and  three 
of  them  were  found  after  24  hrs.  with  all  their  tentacles  and 
blades  closely  inflected,  whilst  the  fourth  had  only  a few  ten- 
tacles inflected.  It  will,  however,  be  shown  in  a future  place, 
that  cut-off  leaves  immersed  in  olive  oil  are  powerfully  affected. 

Infusion  and  Decoction  of  Tea, — Drops  of  a strong  infusion  and 
decoction,  as  well  as  of  a rather  weak  decoction,  of  tea  were 
placed  on  ten  leaves,  none  of  which  became  inflected.  I after- 
wards tested  three  of  them  by  adding  bits  of  meat  to  the  drops 
which  still  remained  on  their  discs,  and  when  I examined  them 
after  24  hrs.  they  were  closely  inflected.  The  chemical  principle 
of  tea,  namely  theine,  was  subsequently  tried  and  produced  no 
effect.  The  albuminous  matter  which  the  leaves  must  originally 
have  contained,  no  doubt,  had  been  rendered  insoluble  by  their 
having  been  completely  dried. 

We  thus  see  that,  excluding  the  experiments  with 
water,  sixty-one  leayes  were  tried  with  drops  of  the 


Chap.  V.  EFFECTS  OF  OKGANIC  FLUIDS.  79 

above-named  non-nitrogenous  fluids ; and  the  tentacles 
were  not  in  a single  case  inflected. 

With  respect  to  nitrogenous  fluids,  the  first  which  came  to 
hand  were  tried.  The  experiments  were  made  at  the  same 
time  and  in  exactly  the  same  manner  as  the  foregoing. 
As  it  was  immediately  evident  that  these  fluids  produced  a 
great  effect,  I neglected  in  most  cases  to  record  how  soon  the 
tentacles  became  inflected.  But  this  always  occurred  in  less 
than  24  hrs. ; whilst  the  drops  of  non-nitrogenous  fluids  which 
produced  no  effect  were  observed  in  every  case  during  a 
considerably  longer  period. 

Milk, — ^Drops  were  placed  on  sixteen  leaves,  and  the  tentacles 
of  all,  as  well  as  the  blades  of  several,  soon  became  greatly 
inflected.  The  periods  were  recorded  in  only  three  cases, 
namely,  with  leaves  on  which  unusually  small  drops  had  been 
placed.  Their  tentacles  were  somewhat  inflected  in  45  m. ; 
and  after  7 hrs.  45  m.  the  blades  of  two  were  so  much  curved 
inwards  that  they  formed  little  cups  enclosing  the  drops. 
These  leaves  re-expanded  on  the  third  day.  On  another  occa- 
sion the  blade  of  a leaf  was  much  inflected  in  5 hrs.  after  a 
drop  of  milk  had  been  placed  on  it. 

Human  Urine, — Drops  were  placed  on  twelve  leaves,  and  the 
tentacles  of  all,  with  a single  exception,  became  greatly  inflected. 
Owing,  I presume,  to  differences  in  the  chemical  nature  of  the 
urine  on  different  occasions,  the  time  required  for  the  movements 
of  the  tentacles  varied  much,  but  was  always  effected  in  under 
24  hrs.  In  two  instances  I recorded  that  all  the  exterior  ten- 
tacles were  completely  inflected  in  17  hrs.,  but  not  the  blade  of 
the  leaf. . In  another  case  the  edges  of  a leaf,  after  25  hrs. 
30  m.,  became  so  strongly  inflected  that  it  was  converted  into  a 
cup.  The  power  of  urine  does  not  lie  in  the  urea,  which,  as 
we  shall  hereafter  see,  is  inoperative. 

Albumen  (fresh  from  a hen’s  egg),  placed  on  seven  leaves, 
caused  the  tentacles  of  six  of  them  to  be  well  inflected.  In  one 
case  the  edge  of  the  leaf  itself  became  much  curled  in  after 
20  hrs.  The  one  leaf  which  was  unaffected  remained  so  for 
26  hrs.,  and  was  then  treated  with  a drop  of  milk,  and  this 
caused  the  tentacles  to  bend  inwards  in  12  hrs. 

Cold  Filtered  Inf  usion  of  Raw  Meat. — This  was  tried  only  on  a 
single  leaf,  which  had  most  of  its  outer  tentacles  and  the  blade 
inflected  in  19  hrs.  During  subsequent  years,  I repeatedly 
used  this  infusion  to  test  leaves  which  had  been  experimented 


80 


DROSERA  ROTUNDIFOLIA. 


Chap.  V. 


on  with  other  substances,  and  it  was  found  to  act  most  ener- 
getically, but  as  no  exact  account  of  these  trials  was  kept,  they 
are  not  here  introduced. 

Mucus, — Thick  and  thin  mucus  from  the  bronchial  tubes, 
placed  on  three  leaves,  caused  inflection.  A leaf  with  thin 
mucus  had  its  marginal  tentacles  and  blade  somewhat  curved 
inward  in  5 hrs.  30  m.,  and  greatly  so  in  20  hrs.  The  action  of 
this  fluid  no  doubt  is  due  either  to  the  saliva  or  to  some  albu- 
minous matter*  mingled  with  it,  and  not,  as  we  shall  see  in  the 
next  chapter,  to  mucin  or  the  chemical  principle  of  mucus. 

Saliva, — Human  saliva,  when  evaporated,  yieldsf  from  1T4  to 
1T9  per  cent,  of  residue ; and  this  yields  0*25  per  cent,  of  ashes, 
so  that  the  proportion  of  nitrogenous  matter  which  saliva  con- 
tains must  be  small.  Nevertheless,  drops  placed  on  the  discs  of 
eight  leaves  acted  on  them  all.  In  one  case  all  the  exterior  ten- 
tacles, excepting  nine,  were  inflected  in  19  hrs.  30  m. ; in  another 
case  a few  became  so  in  2 hrs.,  and  after  7 hrs.  30  m.  all  those 
situated  near  where  the  drop  lay,  as  well  as  the  blade,  were 
acted  on.  Since  making  these  trials,  I have  many  scores  of 
times  just  touched  glands  with  the  handle  of  my  scalpel  wetted 
with  saliva,  to  ascertain  whether  a leaf  was  in  an  active  condi- 
tion ; for  this  was  shown  in  the  course  of  a few  minutes  by  the 
bending  inwards  of  the  tentacles.  The  edible  nest  of  the  Chinese 
swallow  is  formed  of  matter  secreted  by  the  salivary  glands ; two 
grains  were  added  to  one  ounce  of  distilled  water  (one  part  to  218), 
which  was  boiled  for  several  minutes,  but  did  not  dissolve  the 
whole.  The  usual-sized  drops  were  placed  on  three  leaves,  and 
these  in  1 hr.  30  m.  were  well,  and  in  2 hrs.  15  m.  closely, 
inflected. 

Isinglass, — Drops  of  a solution  about  as  thick  as  milk,  and  of 
a still  thicker  solution,  were  placed  on  eight  leaves,  and  the  ten- 
tacles of  all  became  inflected.  In  one  case  the  exterior  tentacles 
were  well  curved  in  after  6 hrs.  30  m.,  and  the  blade  of  the  leaf 
to  a partial  extent  after  24  hrs.  As  saliva  acted  so  efficiently, 
and  yet  contains  so  small  a proportion  of  nitrogenous  matter,  I 
tried  how  small  a quantity  of  isinglass  would  act.  One  part  was 
dissolved  in  218  parts  of  distilled  water,  and  drops  were  placed 
on  four  leaves.  After  5 hrs.  two  of  these  were  considerably  and 
two  moderately  inflected ; after  22  hrs.  the  former  were  greatly 
and  the  latter  much  more  inflected.  In  the  course  of  48  hrs. 


* Mucus  from  the  air-passages  to  contain  some  albumen, 
is  said  in  Marshall,  ‘ Outlines  of  f Muller’s ‘Elements  of  Physi> 

Physiology,’  vol.  ii.  1867,  p.  364,  logy,’  Eng.  Trans,  vol.  i.  p.  514. 


Chap.  V. 


EFFECTS  OF  ORGANIC  FLUIDS. 


81 


from  the  time  when  the  drops  were  placed  on  the  leaves,  all 
four  had  almost  re-expanded.  They  were  then  given  little  bits 
of  meat,  and  these  acted  more  powerfully  than  the  solution. 
One  part  of  isinglass  was  next  dissolved  in  437  of  water ; the 
fluid  thus  formed  was  so  thin  that  it  could  not  be  distinguished 
from  pure  water.  The  usual-sized  drops  were  placed  on  seven 
leaves,  each  of  which  thus  received  9^0  of  a grain  (‘0295  mg.). 
Three  of  them  were  observed  for  41  hrs.,  but  were  in  no  way 
affected ; the  fourth  and  fifth  had  two  or  three  of  their  exterior 
tentacles  inflected  after  18  hrs.;  the  sixth  had  a few  more; 
and  the  seventh  had  in  addition  the  edge  of  the  leaf  just 
perceptibly  curved  inwards.  The  tentacles  of  the  four  latter 
leaves  began  to  re-expand  after  an  additional  interval  of  only 
8 hrs.  Hence  the  -qIq  of  a grain  of  isinglass  is  sufficient  to  affect 
very  slightly  the  more  sensitive  or  active  leaves.  On  one  of  the 
leaves,  which  had  not  been  acted  on  by  the  weak  solution,  and  on 
another,  which  had  only  two  of  its  tentacles  inflected,  drops  of 
the  solution  as  thick  as  milk  were  placed ; and  next  morning, 
after  an  interval  of  16  hrs.,  both  were  found  with  all  their  ten- 
tacles strongly  inflected. 

Altogether  I experimented  on  sixty-four  leaves 
with  the  above  nitrogenous  fluids,  the  five  leaves 
tried  only  with  the  extremely  weak  solution  of  isin- 
glass not  being  included,  nor  the  numerous  trials 
subsequently  made,  of  which  no  exact  account  was 
kept.  Of  these  sixty-four  leaves,  sixty-three  had  their 
tentacles  and  often  their  blades  well  inflected.  The 
one  which  failed  was  probably  too  old  and  torpid. 
But  to  obtain  so  large  a proportion  of  successful 
cases,  care  must  be  taken  to  select  young  and  active 
leaves.  Leaves  in  this  condition  were  chosen  with 
equal  care  for  the  sixty-one  trials  with  non-nitro- 
genous  fluids  (water  not  included) ; and  we  have  seen 
that  not  one  of  these  was  in  the  least  affected.  We 
may  therefore  safely  conclude  that  in  the  sixty-four 
experiments  with  nitrogenous  fluids  the  inflection  of 
the  exterior  tentacles  was  due  to  the  absorption  of 


82 


DROSEKA  ROTUNDIFOLIA. 


Chat.  V. 


nitrogenous  matter  by  the  glands  of  the  tentacles 
on  the  disc. 

Some  of  the  leaves  which  were  not  affected  by  the 
non-nitrogenous  fluids  were,  as  above  stated,  imme- 
diately afterwards  tested  with  bits  of  meat,  and  were 
thus  proved  to  be  in  an  active  condition.  But  in 
addition  to  these  trials,  twenty-three  of  the  leaves, 
with  drops  of  gum,  syrup,  or  starch,  still  lying  on 
their  discs,  which  had  produced  no  effect  in  the  course 
of  between  24  hrs.  and  48  hrs.,  were  then  tested  with 
drops  of  milk,  urine,  or  albumen.  Of  the  twenty-three 
leaves  thus  treated,  seventeen  had  their  tentacles,  and 
in  some  cases  their  blades,  well  inflected;  but  their 
powers  were  somewhat  impaired,  for  the  rate  of  move- 
ment was  decidedly  slower  than  when  fresh  leaves 
were  treated  with  these  same  nitrogenous  fluids.  V This 
impairment,  as  well  as  the  insensibility  of  six  of  the 
leaves,  may  be  attributed  to  injury  from  exosmose, 
caused  by  the  density  of  the  fluids  placed  on  their 
discs.  I 

The  results  of  a few  other  experiments  with  nitrogenous  fluids 
may  be  here  conveniently  given.  Decoctions  of  some  vegetables, 
known  to  be  rich  in  nitrogen,  were  made,  and  these  acted  like 
animal  fluids.  Thus,  a few  green  peas  were  boiled  for  some  time 
in  distilled  water,  and  the  moderately  thick  decoction  thus  made 
was  allowed  to  settle.  Drops  of  the  superincumbent  fluid  were 
placed  on  four  leaves,  and  when  these  were  looked  at  after 
16  hrs.,  the  tentacles  and  blades  of  all  were  found  strongly 
inflected.  I infer  from  a remark  by  Gerhardt*  that  legumin  is 
present  in  peas  in  combination  with  an  alkali,  forming  an 
incoagulable  solution,”  and  this  would  mingle  with  boiling 
water.  I may  mention,  in  relation  to  the  above  and  following 
experiments,  that  according  to  Schifff  certain  forms  of  albumen 


* Watts*  ‘ Diet,  of  Chemistry,’  Digestion,’  tom.  i.  p.  370 ; tom 
vol.  iii.  p.  568.  ii.  pp.  154,  166,  on  legumin. 

t ‘Lemons  sur  la  Phys.  de  la 


Chap.  V. 


EFFECTS  OF  OKGANIC  FLUIDS. 


83 


exist  which  are  not  coagulated  by  boiling  water,  but  are  con- 
verted into  soluble  peptones. 

On  three  occasions  chopped  cabbage-leaves*  were  boiled  in 
distilled  water  for  1 hr.  or  for  Ij-  hr.;  and  by  decanting  the 
decoction  after  it  had  been  allowed  to  rest,  a pale  dirty  green 
fluid  was  obtained.  The  usual-sized  drops  were  placed  on 
thirteen  leaves.  Their  tentacles  and  blades  were  inflected  after 
4 hrs.  to  a quite  extraordinary  degree.  Next  day  the  protoplasm 
within  the  cells  of  the  tentacles  was  found  aggregated  in  the 
most  strongly  marked  manner.  I also  touched  the  viscid  secre- 
tion round  the  glands  of  several  tentacles  with  minute  drops  of 
the  decoction  on  the  head  of  a small  pin,  and  they  became  well 
inflected  in  a few  minutes.  The  fluid  proving  so  powerful,  one 
part  was  diluted  with  three  of  water,  and  drops  were  placed  on 
the  discs  of  five  leaves ; and  these  next  morning  were  so  much 
acted  on  that  their  blades  were  completely  doubled  over.  We 
thus  see  that  a decoction  of  cabbage-leaves  is  nearly  or  quite  as 
potent  as  an  infusion  of  raw  meat. 

About  the  same  quantity  of  chopped  cabbage-leaves  and  of 
distilled  water,  as  in  the  last  experiment,  were  kept  in  a vessel 
for  20  hrs.  in  a hot  closet,  but  not  heated  to  near  the  boiling- 
point.  Drops  of  this  infusion  were  placed  on  four  leaves.  One 
of  these,  after  23  hrs.,  was  much  inflected ; a second  slightly ; a 
third  had  only  the  submarginal  tentacles  inflected;  and  the 
fourth  was  not  at  all  affected.  The  power  of  this  infusion  is 
therefore  very  much  less  than  that  of  the  decoction ; and  it  is 
clear  that  the  immersion  of  cabbage-leaves  for  an  hour  in  water 
at  the  boiling  temperature  is  much  more  efficient  in  extracting 
matter  which  excites  Drosera  than  immersion  during  many 
hours  in  warm  water.  Perhaps  the  contents  of  the  cells  are 
protected  (as  Schiff  remarks  with  respect  to  legumin)  by  the 
walls  being  formed  of  cellulose,  and  that  until  these  are  rup- 
tured by  boiling- water,  but  little  of  the  contained  albuminous 
matter  is  dissolved.  \We  know  from  the  strong  odour  of  cooked 
cabbage-leaves  that  boiling  water  produces  some  chemical 
change  in  them,  and  that  they  are  thus  rendered  far  more 
digestible  and  nutritious  to  man.\  It  is  therefore  an  interesting 


* The  leaves  of  young  plants,  and  the  outer  leaves  of  mature 
before  the  heart  is  formed,  such  plants  1 * 6 per  cent.  Watts’  ‘ Diet, 
as  were  used  by  me,  contain  2*1  of  Chemistry,’  vol.  i.  p.  653. 
per  cent,  of  albuminous  matter, 


84 


DEOSERA  ROTUNDIFOLIA. 


Chap.  V. 


fact  that  water  at  this  temperature  extracts  matter  from  them 
which  excites  Drosera  to  an  extraordinary  degree. 

Grasses  contain  far  less  nitrogenous  matter  than  do  peas  or 
cabbages.  The  leaves  and  stalks  of  three  common  kinds  were 
chopped  and  boiled  for  some  time  in  distilled  water.  Drops 
of  this  decoction  (after  having  stood  for  24  hrs.)  were  placed 
on  six  leaves,  and  acted  in  a rather  peculiar  manner,  of  which 
other  instances  will  be  given  in  the  seventh  chapter  on  the 
salts  of  ammonia.  After  2 hrs.  30  m.  four  of  the  leaves  had 
their  blades  greatly  inflected,  but  not  their  exterior  tentacles ; 
and  so  it  was  with  all  six  leaves  after  24  hrs.  Two  days  after- 
wards the  blades,  as  well  as  the  few  submarginal  tentacles  which 
had  been  inflected,  all  re-expanded ; and  much  of  the  fluid  on 
their  discs  was  by  this  time  absorbed.  It  appears  that  the  de- 
coction strongly  excites  the  glands  on  the  disc,  causing  the  blade 
to  be  quickly  and  greatly  inflected ; but  that  the  stimulus,  dif- 
ferently from  what  occurs  in  ordinary  cases,  does  not  spread,  or 
only  in  a feeble  degree,  to  the  exterior  tentacles. 

I may  here  add  that  one  part  of  the  extract  of  belladonna 
(procured  from  a druggist)  was  dissolved  in  437  of  water,  and 
drops  were  placed  on  six  leaves.  Next  day  all  six  were  some- 
what inflected,  and  after  48  hrs.  were  completely  re-expanded. 
It  was  not  the  included  atropine  which  produced  this  effect,  for 
I subsequently  ascertained  that  it  is  quite  powerless.  I also 
procured  some  extract  of  hyoscyamus  from  three  shops,  and 
made  infusions  of  the  same  strength  as  before.  Of  these  three 
infusions,  only  one  acted  on  some  of  the  leaves,  which  were 
tried.  Though  druggists  believe  that  all  the  albumen  is  pre- 
cipitated in  the  preparation  of  these  drugs,  I cannot  doubt  that 
some  is  occasionally  retained ; and  a trace  would  be  sufficient 
to  excite  the  more  sensitive  leaves  of  Drosera. 


Chap.  YL 


DIGESTION. 


85 


/ 

CHAPTEE  VI. 

The  Digestive  Power  op  the  Secretion  of  Drosera. 

The  secretion  rendered  acid  by  the  direct  and  indirect  excitement  of 
the  glands  — Nature  of  the  acid  — Digestible  substances  — Albu- 
men, its  digestion  arrested  by  alkalies,  recommences  by  the  addi- 
tion of  an  acid  — Meat  — Fibrin  — Syntonin  — Areolar  tissue  — 
Cartilage  — Fibro-cartilage — Bone — Enamel  and  dentine — Phos- 
phate of  lime  — Fibrous  basis  of  bone  — Gelatine  — Chondrin  — 
Milk,  casein  and  cheese  — Gluten  — Legumin  — Pollen  — Globulin 
— Haematin  — Indigestible  substances  — Epidermic  productions  — 
Fibro-elastic  tissue  — Mucin  — Pepsin  — Urea  — Chitine  — Cellu- 
lose — Gun-cotton  — Chlorophyll  — Fat  and  oil  — Starch  — Action 
of  the  secretion  on  living  seeds  — Summary  and  concluding 
remarks. 

As  we  have  seen  that  nitrogenous  fluids  act  very 
differently  on  the  leaves  of  Drosera  from  non-nitro- 
genous  fluids,  and  as  the  leaves  remain  clasped  for  a 
much  longer  time  over  various  organic  bodies  than 
over  inorganic  bodies,  such  as  bits  of  glass,  cinder, 
wood,  &c.,  it  becomes  an  interesting  inquiry,  whether 
they  can  only  absorb  matter  already  in  solution,  or 
render  it  soluble, — that  is,  have  the  power  of  digestion. 
We  shall  immediately  see  that  they  certainly  have  this 
power,  and  that  they  act  on  albuminous  compounds  in 
exactly  the  same  manner  as  does  the  gastric  juice  of 
mammals ; the  digested  matter  being  afterwards  ab- 
sorbed. This  fact,  which  will  be  clearly  proved,  is  a 
wonderful  one  in  the  physiology  of  plants.  I must 
here  state  that  I have  been  aided  throughout  all  my 
later  experiments  by  many  valuable  suggestions  and 
assistance  given  me  with  the  greatest  kindness  by 
Dr.  Burden  Sanderson. 


86 


DKOSERA  ROTUNDIFOLIA. 


Chap.  VI. 


It  may  be  well  to  premise  for  the  sake  of  any  reader 
who  knows  nothing  about  the  digestion  of  albuminous 
compounds  by  animals  that  this  is  effected  by  means 
of  a ferment,  pepsin,  together  with  weak  hydrochloric 
acid,  though  almost  any  acid  will  serve.  Yet  neither 
pepsin  nor  an  acid  by  itself  has  any  such  power.* 
J' We  have  seen  that  when  the  glands  of  the  disc  are 
excited  by  the  contact  of  any  object,  especially  of 
one  containing  nitrogenous  matter,  the  outer  ten- 
tacles and  often  the  blade  become  inflected  ; the  leaf 
being  thus  converted  into  a temporary  cup  or  sto- 
mach. At  the  same  time  the  discal  glands  secrete 
more  copiously,  and  the  secretion  becomes  acid. 
Moreover,  they  transmit  some  influence  to  the  glands 
of  the  exterior  tentacles,  causing  them  to  pour  forth 
a more  copious  secretion,  which  also  becomes  acid  or 
more  acid  than  it  was  before.  \ 

As  this  result  is  an  important  one,  I will  give  the 
evidence.  The  secretion  of  many  glands  on  thirty 
leaves,  which  had  not  been  in  any  way  excited,  was 
tested  with  litmus  paper  ; and  the  secretion  of  twenty- 
two  of  these  leaves  did  not  in  the  least  affect  the  colour, 
whereas  that  of  eight  caused  an  exceedingly  feeble 
and  sometimes  doubtful  tinge  of  red.  Two  other 
old  leaves,  however,  which  appeared  to  have  been  in- 
flected several  times,  acted  much  more  decidedly  on 
the  paper.  Particles  of  clean  glass  were  then  placed 
on  five  of  the  leaves,  cubes  of  albumen  on  six,  and 
bits  of  raw  meat  on  three,  on  none  of  which  was  the 
secretion  at  this  time  in  the  least  acid.  • After  an 
interval  of  24  hrs.,  when  almost  all  the  tentacles  on 


* It  appears,  however,  accord-  though  slowly,  a very  minute 
ing  to  Schiff,  and  contrary  to  the  quantity  of  coagulated  albumen, 
opinion  of  some  physiologists,  Schiff,  ‘Phys.  de  la  Digestion,* 
that  weak  hydrochloric  dissolves,  tom.  ii.  1867,  p.  25 


Chap.  VI. 


DIGESTION. 


87 


these  fourteen  leaves  had  become  more  or  less  in- 
flected, I again  tested  the  secretion,  selecting  glands 
which  had  not  as  yet  reached  the  centre  or  touched 
any  object,  and  it  was  now  plainly  acid.  The  degree 
of  acidity  of  the  secretion  varied  somewhat  on  the 
glands  of  the  same  leaf.  On  some  leaves,  a few  ten- 
tacles did  not,  from  some  unknown  cause,  become  in- 
flected, as  often  happens ; and  in  five  instances  their 
secretion  was  found  not  to  be  in  the  least  acid; 
whilst  the  secretion  of  the  adjoining  and  inflected 
tentacles  on  the  same  leaf  was  decidedly  acid.  With 
leaves  excited  by  particles  of  glass  placed  on  the 
central  glands,  the  secretion  which  collects  on  the 
disc  beneath  them  was  much  more  strongly  acid 
than  that  poured  forth  from  the  exterior  tentacles, 
which  were  as  yet  only  moderately  inflected.  When 
bits  of  albumen  (and  this  is  naturally  alkaline),  or 
bits  of  meat  were  placed  on  the  disc,  the  secretion 
collected  beneath  them  was  likewise  strongly  acid. 
As  raw  meat  moistened  with  water  is  slightly  acid,  I 
compared  its  action  on  litmus  paper  before  it  was 
placed  on  the  leaves,  and  afterwards  when  bathed  in 
the  secretion ; and  there  could  not  be  the  least  doubt 
that  the  latter  was  very  much  more  acid.  I have 
indeed  tried  hundreds  of  times  the  state  of  the  secre- 
tion on  the  discs  of  leaves  which  were  inflected  over 
various  objects,  and  never  failed  to  find  it  acid.  We 
may,  therefore,  conclude  that  the  secretion  from  un- 
excited leaves,  though  extremely  viscid,  is  not  acid  or 
only  slightly  so,  but  that  it  becomes  acid,  or  much 
more  strongly  so,  after  the  tentacles  have  begun  to 
bend  over  any  inorganic  or  organic  object ; and  still 
more  strongly  acid  after  the  tentacles  have  remained 
for  some  time  closely  clasped  over  any  object. 

I may  .here  remind  the  reader  that  the  secretion 
5 


88 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


appears  to  be  to  a certain  extent  antiseptic,  as  it 
checks  the  appearance  of  mould  and  infusoria,  thus 
preventing  for  a time  the  discoloration  and  decay  of 
such  substances  as  the  white  of  an  egg,  cheese,  &c. 
It  therefore  acts  like  the  gastric  juice  of  the  higher 
animals,  which  is  known  to  arrest  putrefaction  by 
destroying  the  microzymes. 


As  I was  anxious  to  leam  what  acid  the  secretion  contained, 
445  leaves  were  washed  in  distilled  water,  given  me  by  Prof. 
Frankland;  but  the  secretion  is  so  viscid  that  it  is  scarcely 
possible  to  scrape  or  wash  off  the  whole.  The  conditions 
were  also  unfavourable,  as  it  was  late  in  the  year  and  the 
leaves  were  small.  Prof.  Frankland  with  great  kindness  under-  ■ 
took  to  test  the  fluid  thus  collected.  The  leaves  were  excited 
by  clean  particles  of  glass  placed  on  them  24  hrs.  previously. 
No  doubt  much  more  acid  would  have  been  secreted  had  the 
leaves  been  excited  by  animal  matter,  but  this  would  have 
rendered  the  analysis  more  difficult.  Prof.  Frankland  informs 
me  that  the  fluid  contained  no  trace  of  hydrochloric,  sulphuric,  ^ 
tartaric,  oxalic,  or  formic  acids.  This  having  been  ascertained,  , 
the  remainder  of  the  fluid  was  evaporated  nearly  to  dryness,  and 
acidified  with  sulphuric  acid;  it  then  evolved  volatile  acid 
vapour,  which  was  condensed  and  digested  with  carbonate  of 
silver.  “ The  weight  of  the  silver  salt  thus  produced  was  only  ; 
*37  gr.,  much  too  small  a quantity  for  the  accurate  determina-  , 
tion  of  the  molecular  weight  of  the  acid.  The  number  obtained,  ] 
however,  corresponded  nearly  with  that  of  propionic  acid ; and  I 
I believe  that  this,  or  a mixture  of  acetic  and  butyric  acids,  were  : 
present  in  the  liquid.  The  acid  doubtless  belongs  to  the  acetic  t 
or  fatty  series.^^  1 

Prof.  Frankland,  as  well  as  his  assistant,  observed  (and  this 
is  an  important  fact)  that  the  fluid,  when  acidified  with  sul- 
phuric acid,  emitted  a powerful  odour  like  that  of  pepsin.” 
The  leaves  from  which  the  secretion  had  been  washed  were 
also  sent  to  Prof.  Frankland;  they  were  macerated  for  some 
hours,  then  acidified  with  sulphuric  acid  and  distilled,  but  no 
acid  passed  over,  r Therefore  the  acid  which  fresh  leaves  con- 
tain, as  shown  by  their  discolouring  litmus  paper  when  crushed, 
must  be  of  a different  nature  from  that  present  in  the  secretion. 
Nor  was  any  odour  of  pepsin  emitted  by  them.  ’• 


Chap.  VI. 


DIGESTION. 


89 


Although  it  has  long  been  known  that  pepsin  with  acetic 
acid  has  the  power  of  digesting  albuminous  comx)ounds, 
it  appeared  advisable  to  ascertain  whether  acetic  acid  could 
be  replaced,  without  the  loss  of  digestiyo  power,  by  the 
allied  acids  which  are  believed  to  occur  in  the  secretion 
of  Drosera,  namely,  propionic,  butyric,  or  valerianic.  Dr. 
Burdon  Sanderson  was  so  kind  as  to  make  for  me  the  follow- 
ing experiments,  the  results  of  which  are  valuable,  indepen- 
dently of  the  present  inquiry.  Prof.  Frankland  supplied  the 
acids. 

" 1.  The  purpose  of  the  following  experiments  was  to  deter- 
mine the  digestive  activity  of  liquids  containing  pepsin,  when 
acidulated  with  certain  volatile  acids  belonging  to  the  acetic 
series,  in  comparison  with  liquids  acidulated  with  hydrochloric 
acid,  in  proportion  similar  to  that  in  which  it  exists  in  gastric 
juice. 

**  2.  It  has  been  determined  empirically  that  the  best  results 
are  obtained  in  artificial  digestion  when  a liquid  containing  two 
per  thousand  of  hydrochloric  acid  gas  by  weight  is  used.  This 
corresponds  to  about  6*25  cubic  centimetres  per  litre  of  ordinary 
strong  hydrochloric  acid.  The  quantities  of  propionic,  butyric, 
and  valerianic  acids  respectively  which  are  required  to  neutralise 
as  much  base  as  6*25  cubic  centimetres  of  HCl,  are  in  grammes 
4*04  of  propionic  acid,  4*82  of  butyric  acid,  and  5*68  of  valerianic 
acid.  It  was  therefore  judged  expedient,  in  comparing  the 
digestive  powers  of  these  acids  with  that  of  hydrochloric  acid,  to 
use  them  in  these  proportions. 

‘‘3.  Five  hundred  cub.  cent,  of  a liquid  containing  about 
8 cub.  cent,  of  a glycerine  extract  of  the  mucous  membrane  of 
the  stomach  of  a dog  killed  during  digestion  having  been  pre- 
pared, 10  cub.  cent,  of  it  were  evaporated  and  dried  at  110°. 
This  quantity  yielded  0*0031  of  residue. 

“4.  Of  this  liquid  four  quantities  were  taken  which  were 
severally  acidulated  with  hydrochloric,  propionic,  butyric,  and 
valerianic  acids,  in  the  proportions  above  indicated.  Each 
liquid  was  then  placed  in  a tube,  which  was  allowed  to  float  in 
a water  bath,  containing  a thermometer  which  indicated  a 
temperature  of  38°  to  40°  Cent.  Into  each,  a quantity  of  un- 
boiled fibrin  was  introduced,  and  the  whole  allowed  to  stand 
for  four  hours,  the  temperature  being  maintained  during  the 
whole  time,  and  care  being  taken  that  each  contained  through- 
out an  excess  of  fibrin.  At  the  end  of  the  period  each  liquid 
was  filtered.  Of  the  filtrate,  which  of  course  contained  as 
much  of  the  fibrin  as  had  been  digested  during  the  four  hours. 


90 


DEOSERA  ROTUNDIFOLIA. 


Chap.  VI. 


10  cub.  cent,  were  measured  out  and  evaporated,  and  dried  at 
110°  as  before.  The  residues  were  respectively — 

**  In  the  liquid  containing  hydrochloric  acid  0*4079 
„ ' „ propionic  acid  0*0601 

„ „ butyric  acid  0*1468 

„ „ valerianic  acid  0*1254 

Hence,  deducting  from  each  of  these  the  above-mentioned 
residue,  left  when  the  digestive  liquid  itself  was  evaporated, 
viz.  0*0031,  we  have, 


''  For  propionic  acid 0*0570 

„ butyric  acid  . . . . . . . . 0*1437 

„ valerianic  acid 0*1223 


as  compared  with  0*4048  for  hydrocliloric  acid;  these  several 
numbers  expressing  the  quantities  of  fibrin  by  weight  digested 
in  presence  of  equivalent  quantities  of  the  respective  acids 
under  identical  conditions. 

''  The  results  of  the  experiment  may  be  stated  thus  : — If  100 
represent  the  digestive  power  of  a liquid  containing  pepsin  with 
the  usual  proportion  of  hydrochloric  acid,  14*0,  35*4,  and  30*2, 
will  represent  respectively  the  digestive  powers  of  the  three 
acids  under  investigation. 

5.  In  a second  experiment  in  which  the  procedure  was  in 
every  respect  the  same,  excepting  that  all  the  tubes  were 
plunged  into  the  same  water-bath,  and  the  residues  dried  at 
115°  C.,  the  results  were  as  follows : — 

Quantity  of  fibrin  dissolved  in  four  hours  by  10  cub.  cent, 
of  the  liquid — 

Propionic  acid  ..  ..  ..  0*0563 

Butyric  acid  ..  ..  ..  0*0835 

Valerianic  acid  ..  ..  ..  0*0615 

♦""The  quantity  digested  by  a similar  liquid  containing 
hydrochloric  acid  was  0*3376.  Hence,  taking  this  as  100,  the 
following  numbers  represent  the  relative  quantities  digested 
by  the  other  acids : 


Propionic  acid  .. 

16-5 

Butyric  acid 

24-7 

Valerianic  acid  .. 

161 

'"  6.  A third  experiment  of  the  same  kind  gave : 


Chap.  VI. 


DIGESTION. 


91 


Quantity  of  fibrin  digested  in  four  hours  by  10  cub.  cent, 
of  the  liquid : 


Hydrochloric  acid 
Propionic  acid  .. 
Butyric  acid 
Valerianic  acid  .. 


0-2915 

0-1490 

0-1044 

0-0520 


Comparing,  as  before,  the  three  last  numbers  with  the  first 
taken  as  100,  the  digestive  power  of  propionic 
sented  by  16-8;  that  of  butyric  acid  by 
valerianic  by  17*8. 

" The  mean  of  these  three  sets  of 
acid  being  taken  as  100)  gives  for 

" Propionic  acid  .. 

Butyric  acid 
Valerianic  acid  .. 


7.  A further  experiment  was  made  to  ascertain  whether  the 
digestive  activity  of  butyric  acid  (which  was  selected  as  being 
apparently  the  most  efficacious)  was  relatively  greater  at  ordinary 
temperatures  than  at  the  temperature  of  the  body.  It  was 
found  that  whereas  10  cub.  cent,  of  a liquid  containing  the  ordi- 
nary proportion  of  hydrochloric  acid  digested  0-1311  gramme, 
a similar  liquid  prepared  with  butyric  acid  digested  0-0455 
gramme  of  fibrin. 

**  Hence,  taking  the  quantities  digested  with  hydrochloric  acid 
at  the  temperature  of  the  body  as  100,  we  have  the  digestive 
power  of  hydrochloric  acid  at  the  temperature  of  16°  to  18° 
Cent,  represented  by  44-9;  that  of  butyric  acid  at  the  same 
temperature  being  15-6.” 


We  here  see  that  at  the  lower  of  these  two  temperatures, 
hydrochloric  acid  with  pepsin  digests,  within  the  same  time, 
rather  less  than  half  the  quantity  of  fibrin  compared  with 
what  it  digests  at  the  higher  temperature;  and  the  power  of 
butyric  acid  is  reduced  in  the  same  proportion  under  similar 
conditions  and  temperatures.  We  have  also  seen  that  butyric 
acid,  which  is  much  more  efficacious  than  propionic  or  vale- 
rianic acids,  digests  with  pepsin  at  the  higher  temperature  less 
than  a third  of  the  fibrin  which  is  digested  at  the  same  tempera- 
ture by  hydrochloric  acid. 


92 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


I will  now  give  in  detail  my  experiments  on  the 
digestive  power  of  the  secretion  of  Drosera,  dividing 
the  substances  tried  into  two  series,  namely  those 
which  are  digested  more  or  less  completely,  and  those 
which  are  not  digested.  We  shall  presently  see  that 
all  these  substances  are  acted  on  by  the  gastric  juice 
of  the  higher  animals  in  the  same  manner.  I beg 
leave  to  call  attention  to  the  experiments  under  the 
head  albumen,  showing  that  the  secretion  loses  its 
power  when  neutralised  by  an  alkali,  and  recovers  it 
when  an  acid  is  added. 

Substances  which  are  comjpletely  or  partially  digested  by 
the  Secretion  of  Drosera. 

Albumen. — After  having  tried  various  substances. 
Dr.  Burdon  Sanderson  suggested  to  me  the  use  of  cubes 
of  coagulated  albumen  or  hard-boiled  egg.  I may  pre- 
mise that  five  cubes  of  the  same  size  as  those  used  in 
the  following  experiments  were  placed  for  the  sake  of 
comparison  at  the  same  time  on  wet  moss  close  to  the 
plants  of  Drosera.  The  weather  was  hot,  and  after  four 
days  some  of  the  cubes  were  discoloured  and  mouldy, 
with  their  angles  a little  rounded ; but  they  were  not 
surrounded  by  a zone  of  transparent  fluid  as  in  the 
case  of  those  undergoing  digestion.  Other  cubes 
retained  their  angles  and  white  colour.  After  eight 
days  all  were  somewhat  reduced  in  size,  discoloured, 
with  their  angles  much  rounded.  Nevertheless  in 
four  out  of  the  five  specimens,  the  central  parts  were 
still  white  and  opaque.  So  that  their  state  differed 
widely,  as  we  shall  see,  from  that  of  the  cubes  sub- 
jected to  the  action  of  the  secretion. 

Experiment  1.  — Bather  large  cubes  of  albumen  were  first 
tried;  the  tentacles  were  well  inflected  in  24  hrs.;  after  an 


Ohap.  VI. 


DIGESTION. 


93 


additional  day  the  angles  of  the  cubes  were  dissolved  and 
rounded;*  but  the  cubes  were  too  large,  so  that  the  leaves 
were  injured,  and  after  seven  days  one  died  and  the  others 
were  dying.  Albumen  which  has  been  kept  for  four  or  five 
days,  and  which,  it  may  be  presumed,  has  begun  to  decay 
slightly,  seems  to  act  more  quickly  than  freshly  boiled  eggs. 
As  the  latter  were  generally  used,  I often  moistened  them 
with  a little  saliva,  to  make  the  tentacles  close  more 
quickly. 

Exyeriment  2. — A cube  of  (i-®-  side 

of  an  inch,  or  2*54  mm.,  in  length)  was  placed  on  a leaf,  and 
after  50  hrs.  it  was  converted  into  a sphere  about  of  an  inch 
(1*905  mm.)  in  diameter,  surrounded  by  perfectly  transparent 
fluid.  After  ten  days  the  leaf  re-expanded,  but  there  was  still 
left  on  the  disc  a minute  bit  of  albumen  now  rendered  trans- 
parent. More  albumen  had  been  given  to  this  leaf  than  could 
be  dissolved  or  digested. 

Experiment  3. — Two  cubes  of  albumen  of  of  an  inch 
(1*27  mm.)  were  placed  on  two  leaves.  After  46  hrs.  every 
atom  of  one  was  dissolved,  and  most  of  the  liquefied  matter 
was  absorbed,  the  fluid  which  remained  being  in  this,  as  in  all 
other  cases,  very  acid  and  viscid.  The  other  cube  was  acted 
on  at  a rather  slower  rate. 

Experiment  4. — Two  cubes  of  albumen  of  the  same  size  as 
the  last  were  placed  on  two  leaves,  and  were  converted  in 
50  hrs.  into  two  large  drops  of  transparent  fluid;  but  when 
these  were  removed  from  beneath  the  inflected  tentacles,  and 
viewed  by  reflected  light  under  the  microscope,  fine  streaks  of 
white  opaque  matter  could  be  seen  in  the  one,  and  traces  of 
similar  streaks  in  the  other.  The  drops  were  replaced  on  the 
leaves,  which  re-expanded  after  10  days;  and  now  nothing 
was  left  except  a very  little  transparent  acid  fluid. 

Experiment  5. — This  experiment  was  slightly  varied,  so  that 
the  albumen  might  be  more  quickly  exposed  to  the  action  of  the 
secretioja.  Two  cubes,  each  of  about  ^ of  an  inch  ( * 635  mm.), 
were  placed  on  the  same  leaf,  and  two  similar  cubes  on  another 


* In  all  my  numerous  experi- 
ments on  the  digestion  of  cubes 
of  albumen,  the  angles  and  edges 
were  invariably  first  rounded. 
Now,  Schiff  states  ( ‘ Legons 
phys.  de  la  Digestion,’  vol.  ii. 
1867,  p.  149}  that  this  is  charac- 


teristic of  the  digestion  of  albu- 
men by  the  gastric  juice  of  ani- 
mals. On  the  other  hand,  he 
remarks,  “les  dissolutions,  en 
chimie,  ont  lieu  sur  toute  la  sur- 
face des  corps  en  contact  avec 
Tagent  dissolvant.” 


94 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


leaf.  These  were  examined  after  21  hrs.  30  m.,  and  all  four 
were  found  rounded.  After  46  hrs.  the  two  cubes  on  the  one 
leaf  were  completely  liquefied,  the  fluid  being  perfectly  trans- 
parent; on  the  other  leaf  some  opaque  white  streaks  could 
still  be  seen  in  the  midst  of  the  fluid.  After  72  hrs.  these 
streaks  disappeared,  but  there  was  still  a little  viscid  fluid 
left  on  the  disc;  whereas  it  was  almost  all  absorbed  on  the 
first  leaf.  Both  leaves  were  now  beginning  to  re- expand. 

The  best  and  almost  sole  test  of  the  presence  of 
some  ferment  analogous  to  pepsin  in  the  secretion 
appeared  to  be  to  neutralise  the  acid  of  the  secretion 
with  an  alkali,  and  to  observe  whether  the  process 
of  digestion  ceased;  and  then  to  add  a little  acid 
and  observe  whether  the  process  recommenced.  iThis 
was  done,  and,  as  we  shall  see,  with  success,  but  it 
was  necessary  first  to  try  two  control  experiments ; 
namely,  whether  the  addition  of  minute  drops  of 
water  of  the  same  size  as  those  of  the  dissolved 
alkalies  to  be  used  would  stop  the  process  of  diges- 
tion ; and,  secondly,  whether  minute  drops  of  weak 
hydrochloric  acid,  of  the  some  strength  and  size  as 
those  to  be  used,  would  injure  the  leaves.  The 
two  following  experiments  were  therefore  tried  ^ 

Experiment  6. — Small  cubes  of  albumen  were  put  on  three 
leaves,  and  minute  drops  of  distilled  water  on  the  head  of  a pin 
were  added  two  or  three  times  daily.  These  did  not  in  the 
least  delay  the  process ; for,  after  48  hrs.,  the  cubes  were  com- 
pletely dissolved  on  all  three  leaves.  On  the  third  day  the 
leaves  began  to  re -expand,  and  on  the  fourth  day  all  the  fluid 
was  absorbed. 

Experiment  7. — Small  cubes  of  albumen  were  put  on  two 
leaves,  and  minute  drops  of  hydrochloric  acid,  of  the  strength  of 
one  part  to  437  of  water,  were  added  two  or  three  times.  This 
did  not  in  the  least  delay,  but  seemed  rather  to  hasten,  the 
process  of  digestion ; for  every  trace  of  the  albumen  disappeared 
in  24  hrs.  30  m.  After  three  days  the  leaves  partially  re- 
expanded, and  by  this  time  almost  all  the  viscid  fluid  on  their 
discs  was  absorbed.  It  is  almost  superfluous  to  state  thal 


Chap.  VI. 


DIGESTION. 


95 


cubes  of  albumen  of  the  same  size  as  those  above  used,  left  for 
seven  days  in  a little  hydrochloric  acid  of  the  above  strength, 
retained  all  their  angles  as  perfect  as  ever. 

Experiment  8. — Cubes  of  albumen  (of  2V  of  an  inch,  or  2*54 
mm.)  were  placed  on  live  leaves,  and  minute  drops  of  a solu- 
tion of  one  part  of  carbonate  of  soda  to  437  of  water  were  added 
at  intervals  to  three  of  them,  and  drops  of  carbonate  of  potash 
of  the  same  strength  to  the  other  two.  The  drops  were  given 
on  the  head  of  a rather  large  pin,  and  I ascertained  that 
each  was  equal  to  about  ^ of  a minim  (*0059  ml.),  so  that 
each  contained  only  of  a grain  (*0135  mg.)  of  the  alkali. 
This  was  not  sufficient,  for  after  46  hrs.  all  five  cubes  were 
dissolved. 

Experiment  9. — The  last  experiment  was  repeated  on  four 
leaves,  with  this  difference,  that  drops  of  the  same  solution  of 
carbonate  of  soda  were  added  rather  oftener,  as  often  as  the 
secretion  became  acid,  so  that  it  was  much  more  effectually 
neutralised.  And  now  after  24  hrs.  the  angles  of  three  of 
the  cubes  were  not  in  the  least  rounded,  those  of  the  fourth 
being  so  in  a very  slight  degree.  Drops  of  extremely  weak 
hydrochloric  acid  (viz.  one  part  to  847  of  water)  were  then 
added,  just  enough  to  neutralise  the  alkali  which  was  still 
present ; and  now  digestion  immediately  recommenced,  so  that 
after  23  hrs.  30  m.  three  of  the  cubes  were  completely  dis- 
solved, whilst  the  fourth  was  converted  into  a minute  sphere, 
surrounded  by  transparent  fluid ; and  this  sphere  next  day 
disappeared. 

Experiment  10. — Stronger  solutions  of  carbonate  of  soda  and 
of  potash  were  next  used,  viz.  one  part  to  109  of  water;  and  as 
the  same-sized  drops  were  given  as  before,  each  drop  contained 
ygVo  ^ grain  (*0539  mg.)  of  either  salt.  Two  cubes  of  albu- 
men (each  about  Jq  of  an  inch,  or  *635  mm.)  were  placed  on  the 
same  leaf,  and  two  on  another.  Each  leaf  received,  as  soon  as 
the  secretion  became  slightly  acid  (and  this  occurred  four  times 
within  24  hrs.),  drops  either  of  the  soda  or  potash,  and  the  acid 
was  thus  effectually  neutralised.  The  experiment  now  succeeded 
perfectly,  for  after  22  hrs.  the  angles  of  the  cubes  were  as  sharp 
as  they  were  at  first,  and  we  know  from  experiment  5 that  such 
small  cubes  would  have  been  completely  rounded  within  this 
time  by  the  secretion  in  its  natural  state.  Some  of  the  fluid  was 
now  removed  with  blotting-paper  from  the  discs  of  the  leaves, 
and  minute  drops  of  hydrochloric  acid  of  the  strength  of  one 
part  to  200  of  water  was  added.  Acid  of  this  greater  strengtli 
was  used  as  the  solutions  of  the  alkalies  were  stronger.  The 


96 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


process  of  digestion  now  commenced,  so  that  within  48  hrs.  from 
the  time  when  the  acid  was  given  the  four  cubes  were  not  only 
completely  dissolved,  but  much  of  the  liquefied  albumen  was 
absorbed. 

Experiment  11. — Two  cubes  of  albumen  of  an  inch,  or 
*635  mm.)  were  placed  on  two  leaves,  and  were  treated  with 
alkalies  as  in  the  last  experiment,  and  with  the  same  result ; 
for  after  22  hrs.  they  had  their  angles  perfectly  sharp,  showing 
that  the  digestive  process  had  been  completely  arrested.  I then 
wished  to  ascertain  what  would  be  the  effect  of  using  stronger 
hydrochloric  acid ; so  I added  minute  drops  of  the  strength  of 
1 per  cent.  This  proved  rather  too  strong,  for  after  48  hrs. 
from  the  time  when  the  acid  was  added  one  cube  was  still 
almost  perfect,  and  the  other  only  very  slightly  rounded,  and 
both  were  stained  slightly  pink.  This  latter  fact  shows  that  the 
leaves  were  injured,*  for  during  the  normal  process  of  digestion 
the  albumen  is  not  thus  coloured,  and  we  can  thus  understand 
why  the  cubes  were  not  dissolved. 

From  these  experiments  we  clearly  see  that  the 
secretion  has  the  power  of  dissolving  albumen,  and 
we  further  see  that  if  an  alkali  is  added,  the  process  of 
digestion  is  stopped,  but  immediately  recommences  as 
soon  as  the  alkali  is  neutralised  by  weak  hydrochloric 
acid.  Even  if  I had  tried  no  other  experiments  than 
these,  they  would  have  almost  suflSced  to  prove  that 
the  glands  of  Drosera  secrete  some  ferment  analo- 
gous to  pepsin,  which  in  presence  of  an  acid  gives 
to  the  secretion  its  power  of  dissolving  albuminous 
compounds. 

Splinters  of  clean  glass  were  scattered  on  a large 
number  of  leaves,  and  these  became  moderately  in- 
flected. They  were  cut  off  and  divided  into  three 
lots;  two  of  them,  after  being  left  for  some  time  in 
a little  distilled  water,  were  strained,  and  some  dis- 


* Sachs  remarks  (‘l^raite  de  agents,  allow  all  their  colouring 

Bot.*  1874,  p.  774),  that  cells  matter  to  escape  into  the  sur- 

which  are  killed  by  freezing,  by  rounding  water, 
too  great  heat,  or  by  chemical 


Chap.  VI. 


DIGESTION. 


97 


coloured,  viscid,  slightly  acid  fluid  was  thus  obtained. 
The  third  lot  was  well  soaked  in  a few  drops  of 
glycerine,  which  is  well  known  to  dissolve  pepsin. 
Cubes  of  albumen  (-^V  of  an  inch)  were  now  placed 
in  the  three  fluids  in  watch-glasses,  some  of  which 
were  kept  for  several  days  at  about  90°  Fahr. 
( 32°*2  Cent.),  and  others  at  the  temperature  of  my 
room;  but  none  of  the  cubes  were  dissolved,  the 
angles  remaining  as  sharp  as  ever.  This  fact  pro- 
bably indicates  that  the  ferment  is  not  secreted  until 
the  glands  are  excited  by  the  absorption  of  a minute 
quantity  of  already  soluble  animal  matter, — a con- 
clusion which  is  supported  by  what  we  shall  hereafter 
see  with  respect  to  Dionsea.  Dr.  Hooker  likewise  found 
that,  although  the  fluid  within  the  pitchers  of  Ne- 
penthes possesses  extraordinary  power  of  digestion,  yet 
when  removed  from  the  pitchers  before  they  have 
been  excited  and  placed  in  a vessel,  it  has  no  such 
power,  although  it  is  already  acid;  and  we  can 
account  for  this  fact  only  on  the  supposition  that  the 
proper  ferment  is  not  secreted  until  some  exciting 
matter  is  absorbed. 

On  three  other  occasions  eight  leaves  were  strongly 
excited  with  albumen  moistened  with  saliva;  they 
were  then  cut  ofi*,  and  allowed  to  soak  for  several 
hours  or  for  a whole  day  in  a few  drops  of  glycerine. 
Some  of  this  extract  was  added  to  a little  hydro- 
chloric acid  of  various  strengths  (generally  one  to 
400  of  water),  and  minute  cubes  of  albumen  were 
placed  in  the  mixture.^  In  two  of  these  trials  the 
cubes  were  not  in  the  least  acted  on ; but  in  the  third 


* As  a control  experiment  bits  the  albumen,  as  might  have  been 

of  albumen  were  placed  in  the  expected,  was  not  in  the  least 

«ame  glycerine  with  hydrochloric  affected  after  two  days, 
acid  of  the  same  strength;  and 


98 


DROSEEA  ROTUNDIFOLIA. 


Chap.  VL 


the  experiment  was  successful.  For  in  a vessel  con- 
taining two  cubes,  both  were  reduced  in  size  in  3 hrs. ; 
and  after  24  hrs.  mere  streaks  of  undissolved  albu- 
men were  left.  In  a second  vessel,  containing  two 
minute  ragged  bits  of  albumen,  both  were  likewise 
reduced  in  size  in  3 hrs.,  and  after  24  hrs.  completely 
disappeared.  I then  added  a little  weak  hydro- 
chloric acid  to  both  vessels,  and  placed  fresh  cubes 
of  albumen  in  them;  but  these  were  not  acted  on. 
This  latter  fact  is  intelligible  according  to  the  high 
authority  of  Schiff,*  who  has  demonstrated,  as  he 
believes,  in  opposition  to  the  view  held  by  some 
physiologists,  that  a certain  small  amount  of  pepsin 
is  destroyed  during  the  act  of  digestion.  So  that  if 
my  solution  contained,  as  is  probable,  an  extremely 
small  amount  of  the  ferment,  this  would  have  been 
consumed  by  the  dissolution  of  the  cubes  of  albumen 
first  given;  none  being  left  when  the  hydrochloric 
acid  was  added.  The  destruction  of  the  ferment 
during  the  process  of  digestion,  or  its  absorption  after 
the  albumen  had  been  converted  into  a peptone,  will 
also  account  for  only  one  out  of  the  three  latter  sets 
of  experiments  having  been  successful. 

Digestion  of  Boast  Meat — Cubes  of  about  of  an 
inch  (1*27  mm.)  of  moderately  roasted  meat  were 
placed  on  five  leaves  which  became  in  12  hrs.  closely 
inflected.  After  48  hrs.  I gently  opened  one  leaf,  and 
the  meat  now  consisted  of  a minute  central  sphere, 
partially  digested  and  surrounded  by  a thick  envelope 
of  transparent  viscid  fluid.  The  whole,  without  being 
much  disturbed,  was  removed  and  placed  under  the 
microscope.  In  the  central  part  the  transverse  striae 
on  the  muscular  fibres  were  quite  distinct;  and  it  was 


♦ ‘Lemons  pl'vs.  de  la  Digestion,’  1867,  tom.  ii.  pp.  114-126. 


Chap.  VL 


DIGESTION. 


interesting  to  observe  how  gradually  they  disappeared, 
when  the  same  fibre  was  traced  into  the  surrounding 
fluid.  They  disappeared  by  the  striae  being  replaced 
by  transverse  lines  formed  of  excessively  minute  dark 
points,  which  towards  the  exterior  could  be  seen  only 
under  a very  high  power  ; and  ultimately  these  points 
were  lost.  When  I made  these  observations,  I had 
not  read  Schiff’s  account*  of  the  digestion  of  meat 
by  gastric  juice,  and  I did  not  understand  the  mean- 
ing of  the  dark  points.  But  this  is  explained  in  the 
following  statement,  and  we  further  see  how  closely 
similar  is  the  process  of  digestion  by  gastric  juice  and 
by  the  secretion  of  Drosera. 

On  a dit  que  le  sue  gastrique  faisait  perdre  a la  fibre  muscu- 
laire  ses  stries  transversales.  Ainsi  enoncee,  cette  proposition 
pourrait  donner  lieu  a une  equivoque,  car  ce  qui  se  perd,  ce  n’est 
que  Vaspect  exterieur  de  la  striature  et  non  les  elements  anato- 
miques  qui  la  composent.  On  sait  que  les  stries  qui  donnent  un 
aspect  si  caracteristique  a la  fibre  musculaire,  sont  le  resultat  de 
la  juxtaposition  et  du  parallelisme  des  corpuscules  elementaires, 
places,  a distances  egales,  dans  f interieur  des  fibrilles  contigues. 
Or,  des  que  le  tissu  connectif  qui  relie  entre  elles  les  fibrilles 
elementaires  vient  a se  gonfler  et  a se  dissoudre,  et  que  les 
fibrilles  elles-memes  se  dissocient,  ce  parallelisme  est  detruit  et 
avec  lui  Taspect,  le  phenomene  optique  des  stries.  Si,  apres  la 
desagregation  des  fibres,  on  examine  au  microscope  les  fibrilles 
elementaires,  on  distingue  encore  tres-nettement  a leur  interieur 
les  corpuscules,  et  on  continue  a les  voir,  de  plus  en  plus  pales, 
jusqu’au  moment  ou  les  fibrilles  elles-memes  se  liquefient  et  dis- 
paraissent  dans  le  sue  gastrique.  Ce  qui  constitue  la  striature, 
a proprement  parler,  n’est  done  pas  detruit,  avant  la  lique- 
faction de  la  fibre  ebarnue  elle-meme.” 

In  the  viscid  fluid  surrounding  the  central  sphere  of 
undigested  meat  there  were  globules  of  fat  and  little 
bits  of  fibro-elastic  tissue ; neither  of  which  were  in 


* ‘ Lemons  pbys.  de  la  Digestion,’  tom.  ii.  p.  145. 


100 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI 


the  least  digested.  There  were  also  little  free  paral- 
lelograms of  yellowish,  highly  translucent  matter. 
Schifif,  in  speaking  of  the  digestion  of  meat  by  gastric 
juice,  alludes  to  such  parallelograms,  and  says : — 

''  Le  gonflement  par  lequel  commence  la  digestion  de  la  viande, 
resulte  de  Taction  du  sue  gastrique  acide  sur  le  tissu  connectif 
qui  se  dissout  d’abord,  et  qui,  par  sa  liquefaction,  desagrege  les 
fibrilles.  Celles-ci  se  dissolvent  ensuite  en  grande  partie,  mais, 
avant  de  passer  a Tetat  liquide,  elles  tendent  a se  briser  en 
petits  fragments  transversaux.  Les  ^ sarcous  elements*  de 
Bowman,  qui  ne  sont  autre  chose  que  les  produits  de  cette 
division  transversale  des  fibrilles  elementaires,  peuvent  etre 
prepares  et  isoles  a Taide  du  sue  gastrique,  pourvu  qu’on 
n’attend  pas  jusqu’a  la  liquefaction  complete  du  muscle.” 

After  an  interval  of  72  hrs.,  from  the  time  when 
the  five  cubes  were  placed  on  the  leaves,  I opened  the 
four  remaining  ones.  On  two  nothing  could  be  seen 
but  little  masses  of  transparent  viscid  fluid ; but 
when  these  were  examined  under  a high  power, 
fat-globules,  bits  of  fibro-elastic  tissue,  and  some  few 
parallelograms  of  sarcous  matter,  could  be  distin- 
guished, but  not  a vestige  of  transverse  striae.  On  the 
other  two  leaves  there  were  minute  spheres  of  only 
partially  digested  meat  in  the  centre  of  much  trans- 
parent fluid. 

Fibrin. — Bits  of  fibrin  were  left  in  water  during 
four  days,  whilst  the  following  experiments  were 
tried,  but  they  were  not  in  the  least  acted  on.  The 
fibrin  which  I first  used  was  not  pure,  and  included 
dark  particles : it  had  either  not  been  well  prepared 
or  had  subsequently  undergone  some  change.  Thin 
portions,  about  of  an  inch  square,  were  placed 
on  several  leaves,  and  though  the  fibrin  was  soon 
liquefied,  the  whole  was  never  dissolved.  Smaller 
particles  were  then  placed  on  four  leaves,  and  minute 


Chap.  VI. 


DIGESTION. 


101 


drops  of  hydrochloric  acid  (one  part  to  437  of 
water)  were  added ; this  seemed  to  hasten  the  process 
of  digestion,  for  on  one  leaf  all  was  liquefied  and 
absorbed  after  20  hrs. ; but  on  the  three  other  leaves 
some  undissolved  residue  was  left  after  48  hrs.  It 
is  remarkable  that  in  all  the  above  and  following 
experiments,  as  well  as  when  much  larger  bits  of 
fibrin  were  used,  the  leaves  were  very  little  excited ; 
and  it  was  sometimes  necessary  to  add  a little  saliva 
to  induce  complete  inflection.  The  leaves,  moreover, 
began  to  re-expand  after  only  48  hrs.,  whereas  they 
would  have  remained  inflected  for  a much  longer 
time  had  insects,  meat,  cartilage,  albumen,  &c.,  been 
placed  on  them. 

I then  tried  some  pure  white  fibrin,  sent  me  by  Dr. 
Burden  Sanderson. 

Experiment  1. — Two  particles,  barely  of  an  incli  (1‘27  mm.) 
square,  were  placed  on  opposite  sides  of  the  same  leaf.  One  of 
these  did  not  excite  the  surrounding  tentacles,  and  the  gland 
on  which  it  rested  soon  dried.  The  other  particle  caused  a few 
of  the  short  adjoining  tentacles  to  be  inflected,  the  more  distant 
ones  not  being  affected.  After  21  hrs.  both  were  almost,  and 
after  72  hrs.  completely,  dissolved. 

Experiment  2. — The  same  experiment  with  the  same  result, 
only  one  of  the  two  bits  of  fibrin  exciting  the  short  surround- 
ing tentacles.  This  bit  was  so  slowly  acted  on  that  after  a 
day  I pushed  it  on  to  some  fresh  glands.  In  three  days  from 
the  time  when  it  was  first  placed  on  the  leaf  it  was  completely 
dissolved. 

Experiment  3. — Bits  of  fibrin  of  about  the  same  size  as  before 
were  placed  on  the  discs  of  two  leaves ; these  caused  very  little 
inflection  in  23  hrs.,  but  after  48  hrs.  both  were  well  clasped  by 
the  surrounding  short  tentacles,  and  after  an  additional  24  hrs. 
were  completely  dissolved.  On  the  disc  of  one  of  these  leaves 
much  clear  acid  fluid  was  left. 

Experiment  4. — Similar  bits  of  fibrin  were  placed  on  the  discs 
of  two  leaves;  as  after  2 hrs.  the  glands  seemed  rather  dry, 
they  were  freely  moistened  with  saliva;  this  soon  caused 
strong  inflection  both  of  the  tentacles  and  blades,  with  copious 


102 


DKOSERA  ROTUNDIFOLIA. 


Chap.  VI 


secretion  from  the  glands.  In  18  hrs.  the  fibrin  was  com- 
pletely  liquefied,  but  undigested  atoms  still  floated  in  the 
liquid;  these,  however,  disappeared  in  under  two  additional 
days. 

From  these  experiments  it  is  clear  that  the  secre- 
tion completely  dissolves  pure  fibrin.  The  rate  of 
dissolution  is  rather  slow;  but  this  depends  merely 
on  this  substance  not  exciting  the  leaves  sufficiently, 
so  that  only  the  immediately  adjoining  tentacles  are 
inflected,  and  the  supply  of  secretion  is  small. 

Syntonin, — This  substance,  extracted  from  muscle, 
was  kindly  prepared  for  me  by  Dr.  Moore.  Very 
differently  from  fibrin,  it  acts  quickly  and  energetic- 
ally. Small  portions  placed  on  the  discs  of  three 
leaves  caused  their  tentacles  and  blades  to  be  strongly 
inflected  within  8 hrs. ; but  no  further  observations 
were  made.  It  is  probably  due  to  the  presence  of 
this  substance  that  raw  meat  is  too  powerful  a stimu- 
lant, often  injuring  or  even  killing  the  leaves. 

Areotar  Tissue. — Small  portions  of  this  tissue  from  a 
sheep  were  placed  on  the  discs  of  three  leaves  ; these 
became  moderately  well  inflected  in  24  hrs.,  but  began 
to  re-expand  after  48  hrs.,  and  were  fully  re-expanded 
in  72  hrs.,  always  reckoning  from  the  time  when  the 
bits  were  first  given.  This  substance,  therefore,  like 
fibrin,  excites  the  leaves  for  only  a short  time.  The 
residue  left  on  the  leaves,  after  they  were  fully  re- 
expanded, was  examined  under  a high  power  and 
found  much  altered,  but,  owing  to  the  presence  of  a 
quantity  of  elastic  tissue,  which  is  never  acted  on, 
could  hardly  be  said  to  be  in  a liquefied  condition. 

Some  areolar  tissue  free  from  elastic  tissue  was  next 
procured  from  the  visceral  cavity  of  a toad,  and 
moderately  sized,  as  well  as  very  small,  bits  were 
placed  on  five  leaves.  After  24  hrs.  two  of  the  bits 


Chap.  VI. 


DIGESTION. 


103 


were  completely  liquefied;  two  others  were  rendered 
transparent,  but  not  quite  liquefied;  whilst  the  fifth 
was  but  little  affected.  Several  glands  on  the  three 
latter  leaves  were  now  moistened  with  a little  saliva, 
which  soon  caused  much  inflection  and  secretion, 
with  the  result  that  in  the  course  of  12  additional 
hrs.  one  leaf  alone  showed  a remnant  of  undigested 
tissue.  On  the  discs  of  the  four  other  leaves  (to  one 
of  which  a rather  large  bit  had  been  given)  nothing 
was  left  except  some  transparent  viscid  fluid.  I may 
add  that  some  of  this  tissue  included  points  of  black 
pigment,  and  these  were  not  at  all  affected.  As  a 
control  experiment,  small  portions  of  this  tissue  were 
left  in  water  and  on  wet  moss  for  the  same  length  of 
time,  and  remained  white  and  opaque.  From  these 
facts  it  is  clear  that  areolar  tissue  is  easily  and 
quickly  digested  by  the  secretion;  but  that  it  does 
not  greatly  excite  the  leaves. 

Cartilage. — Three  cubes  (-^V  of  an  inch  or  1-27  mm.) 
of  white,  translucent,  extremely  tough  cartilage  were 
cut  from  the  end  of  a slightly  roasted  leg-bone  of  a 
sheep.  These  were  placed  on  three  leaves,  borne  by 
poor,  small  plants  in  my  greenhouse  during  Novem- 
ber ; and  it  seemed  in  the  highest  degree  improbable 
that  so  hard  a substance  would  be  digested  under 
such  unfavourable  circumstances.  Nevertheless,  after 
48  hrs.,  the  cubes  were  largely  dissolved  and  con- 
verted into  minute  spheres,  surrounded  by  trans- 
parent, very  acid  fluid.  Two  of  these  spheres  were 
completely  softened  to  their  centres ; whilst  the  third 
still  contained  a very  small  irregularly  shaped  core 
of  solid  cartilage.  Their  surfaces  were  seen  under 
the  microscope  to  be  curiously  marked  by  prominent 
ridges,  showing  that  the  cartilage  had  been  un- 
equally corroded  by  the  secretion.  I need  hardly 


104 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


say  that  cubes  of  the  same  cartilage,  kept  in  water 
for  the  same  length  of  time,  were  not  in  the  least 
affected. 

During  a more  favourable  season,  moderately  sized 
bits  of  the  skinned  ear  of  a cat,  which  includes 
cartilage,  areolar  and  elastic  tissue,  were  placed  on 
three  leaves.  Some  of  the  glands  were  touched  with 
saliva,  which  caused  prompt  inflection.  Two  of  the 
leaves  began  to  re-expand  after  three  days,  and  the 
third  on  the  fifth  day.  The  fluid  residue  left  on 
their  discs  was  now  examined,  and  consisted  in  one 
case  of  perfectly  transparent,  viscid  matter ; in  the 
other  two  cases,  it  contained  some  elastic  tissue  and 
apparently  remnants  of  half  digested  areolar  tissue. 

Fibro-cartilage  (from  between  the  vertebrae  of  the 
tail  of  a sheep).  Moderately  sized  and  small  bits 
(the  latter  about  of  an  inch)  were  placed  on  nine 
leaves.  Some  of  these  were  well  and  some  very  little 
inflected.  In  the  latter  case  the  bits  were  dragged 
over  the  discs,  so  that  they . were  well  bedaubed . 
with  the  secretion,  and  many  glands  thus  irritated. 
All  the  leaves  re-expanded  after  only  two  days ; so 
that  they  were  but  little  excited  by  this  substance. 
The  bits  were  not  liquefied,  but  were  certainly  in  an 
altered  condition,  being  swollen,  much  more  trans- 
parent, and  so  tender  as  to  disintegrate  very  easily. 
My  son  Francis  prepared  some  artificial  gastric  juice, 
which  was  proved  efficient  by  quickly  dissolving 
fibrin,  and  suspended  portions  of  the  fibro-cartilage 
in  it.  These  swelled  and  became  hyaline,  exactly  like 
those  exposed  to  the  secretion  of  Drosera,  but  were 
not  dissolved.  This  result  surprised  me  much,  as 
two  physiologists  were  of  opinion  that  fibro-cartilage 
would  be  easily  digested  by  gastric  juice.  I there- 
fore asked  Dr.  Klein  to  examine  the  specimens ; and 


CHAP.  VI. 


DIGESTION. 


105 


he  reports  that  the  two  which  had  been  subjected  to 
artificial  gastric  juice  were  ‘‘in  that  state  of  diges- 
tion in  which  we  find  connective  tissue  when  treated 
with  an  acid,  viz.  swollen,  more  or  less  hyaline,  the 
fibrillar  bundles  having  become  homogeneous  and  lost 
their  fibrillar  structure.’’  In  the  specimens  which  had 
been  left  on  the  leaves  of  Drosera,  until  they  re- 
expanded, “parts  were  altered,  though  only  slightly 
so,  in  the  same  manner  as  those  subjected  to  the 
gastric  juice,  as  they  had  become  more  transparent, 
almost  hyaline,  with  the  fibrillation  of  the  bundles 
indistinct.”  Fibro-cartilage  is  therefore  acted  on  in 
nearly  the  same  manner  by  gastric  juice  and  by  the 
secretion  of  Drosera. 

Bone.  — Small  smooth  bits  of  the  dried  hyoidal 
bone  of  a fowl  moistened  with  saliva  were  placed  on 
two  leaves,  and  a similarly  moistened  splinter  of  an 
extremely  hard,  broiled  mutton-chop  bone  on  a third 
leaf.  These  leaves  soon  became  strongly  inflected, 
and  remained  so  for  an  unusual  length  of  time ; 
namely,  one  leaf  for  ten  and  the  other  two  for  nine 
days.  The  bits  of  bone  were  surrounded  all  the  time 
by  acid  secretion.  When  examined  under  a weak 
power,  they  were  found  quite  softened,  so  that  they 
were  readily  penetrated  by  a blunt  needle,  torn  into 
fibres,  or  compressed.  Dr.  Klein  was  so  kind  as  to 
make  sections  of  both  bones  and  examine  them.  He 
informs  me  that  both  presented  the  normal  appearance 
of  decalcified  bone,  with  traces  of  the  earthy  salts 
occasionally  left.  The  corpuscles  with  their  processes 
were  very  distinct  in  most  parts  ; but  in  some  parts, 
especially  near  the  periphery  of  the  hyoidal  bone, 
none  could  be  seen.  Other  parts  again  appeared 
amorphous,  with  even  the  longitudinal  striation  of 
bone  not  distinguishable.  This  amorphous  structure 


106 


DROSERA  ROTUNDIFOLIA. 


Chap.  'VI. 


as  Dr.  Klein  thinks,  may  be  the  result  either  of  the 
incipient  digestion  of  the  fibrous  basis  or  of  all  the 
animal  matter  having  been  removed,  the  corpuscles 
being  thus  rendered  invisible.  A hard,  brittle,  yellow- 
ish substance  occupied  the  position  of  the  medulla 
in  the  fragments  of  the  hyoidal  bone. 

As  the  angles  and  little  projections  of  the  fibrous 
basis  were  not  in  the  least  rounded  or  corroded,  two  of 
the  bits  were  placed  on  fresh  leaves.  These  by  the 
next  morning  were  closely  inflected,  and  remained 
so, — the  one  for  six  and  the  other  for  seven  days, — 
therefore  for  not  so  long  a time  as  on  the  first  occasion, 
but  for  a much  longer  time  than  ever  occurs  with 
leaves  inflected  over  inorganic  or  even  over  many 
organic  bodies.  The  secretion  during  the  whole  time 
coloured  litmus  paper  of  a bright  red ; but  this  may 
have  been  due  to  the  presence  of  the  acid  super- 
phosphate of  lime.  When  the  leaves  re-expanded,  the 
angles  and  projections  of  the  fibrous  basis  were  as 
sharp  as  ever.  I therefore  concluded,  falsely  as  we 
shall  presently  see,  that  the  secretion  cannot  touch 
the  fibrous  basis  of  bone.  The  more  probable  expla- 
nation is  that  the  acid  was  all  consumed  in  decom- 
posing the  phosphate  of  lime  which  still  remained; 
so  that  none  was  left  in  a free  state  to  act  in  con- 
junction with  the  ferment  on  the  fibrous  basis. 

Enamel  and  Dentine, — As  the  secretion  decalcified 
ordinary  bone,  I determined  to  try  whether  it  would 
act  on  enamel  and  dentine,  but  did  not  expect  that  it 
would  succeed  with  so  hard  a substance  as  enamel. 
Dr.  Klein  gave  me  some  thin  transverse  slices  of 
the  canine  tooth  of  a dog;  small  angular  fragments 
of  which  were  placed  on  four  leaves;  and  these  were 
examined  each  succeeding  day  at  the  same  hour.  The 
results  are,  I think,  worth  giving  in  detail. 


Chap.  VI. 


DIGESTION. 


107 


Experimeyit  1. — May  1st,  fragment  placed  on  leaf ; 3rd,  ten- 
tacles but  little  inflected,  so  a little  saliva  was  added ; 6th,  as 
the  tentacles  were  not  strongly  inflected,  the  fragment  was 
transferred  to  another  leaf,  which  acted  at  first  slowly,  but  by 
the  9th  closely  embraced  it.  On  the  11th  this  second  leaf 
began  to  re-expand ; the  fragment  was  manifestly  softened,  and 
Br.  Klein  reports,  ^'a  great  deal  of  enamel  and  the  greater 
part  of  the  dentine  decalcified.’' 

Experiment  2. — May  1st,  fragment  placed  on  leaf ; 2nd,  ten- 
tacles fairly  well  inflected,  with  much  secretion  on  the  disc,  and 
remained  so  until  the  7th,  when  the  leaf  re-expanded.  The 
fragment  was  now  transferred  to  a fresh  leaf,  which  next  day 
(8th)  was  inflected  in  the  strongest  manner,  and  thus  remained 
until  the  11th,  when  it  re-expanded.  Dr.  Klein  reports,  a great 
deal  of  enamel  and  the  greater  part  of  the  dentine  decalcified." 

Experiment  3. — May  1st,  fragment  moistened  with  saliva  and 
placed  on  a leaf,  which  remained  well  inflected  until  5th,  when 
it  re-expanded.  The  enamel  was  not  at  all,  and  the  dentine 
only  slightly,  softened.  The  fragment  was  now  transferred  to  a 
fresh  leaf,  which  next  morning  (6th)  was  strongly  inflected,  and 
remained  so  until  the  11th.  The  enamel  and  dentine  both  now 
somewhat  softened ; and  Dr.  Klein  reports,  **  less  than  half  the 
enamel,  but  the  greater  part  of  the  dentine,  decalcified." 

Experiment  4. — May  1st,  a minute  and  thin  bit  of  dentine, 
moistened  with  saliva,  was  placed  on  a leaf,  which  was  soon 
inflected,  and  re-expanded  on  the  5th.  The  dentine  had  become 
as  flexible  as  thin  paper.  It  was  then  transferred  to  a fresh  leaf, 
which  next  morning  (6th)  was  strongly  inflected,  and  reopened 
on  the  10th.  The  decalcified  dentine  was  now  so  tender  that  it 
was  torn  into  shreds  merely  by  the  force  of  the  re-expanding 
tentacles. 

From  these  experiments  it  appears  that  enamel  is 
attacked  by  the  secretion  with  more  difficulty  than 
dentine,  as  might  have  been  expected  from  its  ex- 
treme hardness ; and  both  with  more  difficulty  than 
ordinary  bone.  After  the  process  of  dissolution  has 
once  commenced,  it  is  carried  on  with  greater  ease ; 
this  may  be  inferred  from  the  leaves,  to  which  the 
fragments  were  transferred,  becoming  in  all  four  cases 
strongly  inflected  in  the  course  of  a single  day ; whereas 
the  first  set  of  leaves  acted  much  less  quickly  and 


108 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI 


energetically.  The  angles  or  projections  of  the  fibrous 
basis  of  the  enamel  and  dentine  (except,  perhaps,  in 
No.  4,  which  could  not  be  well  observed)  were  not  in 
the  least  rounded ; and  Dr.  Klein  remarks  that  their 
microscopical  structure  was  not  altered.  But  this 
could  not  have  been  expected,  as  the  decalcification 
was  not  complete  in  the  three  specimens  which  were 
carefully  examined. 

Fibrous  Basis  of  Bone. — I at  first  concluded,  as 
already  stated,  that  the  secretion  could  not  digest  this 
substance.  I therefore  asked  Dr.  Burdon  Sanderson 
to  try  bone,  enamel,  and  dentine,  in  artificial  gastric 
juice,  and  he  found  that  they  were  after  a considerable 
time  completely  dissolved.  Dr.  Klein  examined  some 
of  the  small  lamellae,  into  which  part  of  the  skull  of  a 
cat  became  broken  up  after  about  a week’s  immersion 
in  the  fluid,  and  he  found  that  towards  the  edges  the 

matrix  appeared  rarified,  thus  producing  the  appear- 
ance as  if  the  canaliculi  of  the  bone-corpuscles  had 
become  larger.  Otherwise  the  corpuscles  and  their 
canaliculi  were  very  distinct.”  So  that  with  bone 
subjected  to  artificial  gastric  juice  complete  de- 
calcification  precedes  the  dissolution  of  the  fibrous 
basis.  Dr.  Burdon  Sanderson  suggested  to  me  that 
the  failure  of  Drosera  to  digest  the  fibrous  basis  of 
bone,  enamel,  and  dentine,  might  be  due  to  the  acid 
being  consumed  in  the  decomposition  of  the  earthy 
salts,  so  that  there  was  none  left  for  the  work  of 
digestion.  Accordingly,  my  son  thoroughly  decal- 
cified the  bone  of  a sheep  with  weak  hydrochloric 
acid;  and  seven  minute  fragments  of  the  fibrous 
basis  were  placed  on  so  many  leaves,  four  of  the 
fragments  being  first  damped  with  saliva  to  aid 
prompt  inflection.  All  seven  leaves  became  inflected, 
but  only  very  moderately,  in  the  course  of  a day. 


Chap.  VI. 


DIGESTION. 


109 


They  quickly  began  to  re-expand ; five  of  them  on 
the  second  day,  and  the  other  two  on  the  third  day. 
On  all  seven  leaves  the  fibrous  tissue  was  converted 
into  perfectly  transparent,  viscid,  more  or  less  lique- 
fied little  masses.  In  the  middle,  however,  of  one, 
my  son  saw  under  a high  power  a few  corpuscles, 
with  traces  of  fibrillation  in  the  surrounding  trans- 
parent matter.  From  these  facts  it  is  clear  that  the 
leaves  are  very  little  excited  by  the  fibrous  basis  of 
bone,  but  that  the  secretion  easily  and  quickly  lique- 
fies it,  if  thoroughly  decalcified.  The  glands  which 
had  remained  in  contact  for  two  or  three  days  with 
the  viscid  masses  were  not  discoloured,  and  appa- 
rently had  absorbed  little  of  the  liquefied  tissue, 
or  had  been  little  affected  by  it. 

Phosphate  of  Lime. — As  we  have  seen  that  the  ten- 
tacles of  the  first  set  of  leaves  remained  clasped  for 
nine  or  ten  days  over  minute  fragments  of  bone,  and 
the  tentacles  of  the  second  set  for  six  or  seven  days 
over  the  same  fragments,  I was  led  to  suppose  that 
it  was  the  phosphate  of  lime,  and  not  any  included 
animal  matter,  which  caused  such  long  continued  in- 
flection. It  is  at  least  certain  from  what  has  just  been 
shown  that  this  cannot  have  been  due  to  the  presence 
of  the  fibrous  basis.  With  enamel  and  dentine 
(the  former  of  which  contains  only  4 per  cent,  of 
organic  matter)  the  tentacles  of  two  successive  sets 
of  leaves  remained  inflected  altogether  for  eleven 
days.  In  order  to  test  my  belief  in  the  potency  of 
phosphate  of  lime,  I procured  some  from  Prof.  Frank- 
land  absolutely  free  of  animal  matter  and  of  any  acid. 
A small  quantity  moistened  with  water  was  placed 
on  the  discs  of  two  leaves.  One  of  these  was  only 
slightly  affected  ; the  other  remained  closely  inflected 
for  ten  days,  when  a few  of  the  tentacles  began  to 


110 


DKOSERA  ROTUNDIFOLIA. 


Chap.  VL 


re-expand,  the  rest  being  much  injured  or  killed.  I 
repeated  the  experiment,  but  moistened  the  phosphate 
with  saliva  to  insure  prompt  inflection ; one  leaf  re- 
mained inflected  for  six  days  (the  little  saliva  used 
would  not  have  acted  for  nearly  so  long  a time)  and 
then  died;  the  other  leaf  tried  to  re-expand  on  the 
sixth  day,  but  after  nine  days  failed  to  do  so,  and 
likewise  died.  Although  the  quantity  of  phosphate 
given  to  the  above  four  leaves  was  extremely  small, 
much  was  left  in  every  case  undissolved.  A larger 
quantity  wetted  with  water  was  next  placed  on  the 
discs  of  three  leaves ; and  these  became  most  strongly 
inflected  in  the  course  of  24  hrs.  They  never  re- 
expanded ; on  the  fourth  day  they  looked  sickly, 
and  on  the  sixth  were  almost  dead.  Large  drops 
of  not  very  viscid  fluid  hung  from  their  edges  during 
the  six  days.  This  fluid  was  tested  each  day  with 
litmus  paper,  but  never  coloured  it ; and  this  cir- 
cumstance I do  not  understand,  as  the  superphosphate 
of  lime  is  acid.  I suppose  that  some  superphosphate 
must  have  been  formed  by  the  acid  of  the  secretion 
acting  on  the  phosphate,  but  that  it  was  all  absorbed 
and  injured  the  leaves;  the  large  drops  which  hung 
from  their  edges  being  an  abnormal  and  dropsical 
secretion.  Anyhow,  it  is  manifest  that  the  phos- 
phate of  lime  is  a most  powerful  stimulant.  Even 
small  doses  are  more  or  less  poisonous,  probably  on 
the  same  principle  that  raw  meat  and  other  nutri- 
tious substances,  given  in  excess,  kill  the  leaves. 
Hence  the  conclusion,  that  the  long  continued  in- 
flection of  the  tentacles  over  fragments  of  bone, 
enamel,  and  dentine,  is  caused  by  the  presence  of 
phosphate  of  lime,  and  not  of  any  included  animal 
matter,  is  no  doubt  correct. 

Gelatine, — I used  pure  gelatine  in  thin  sheets  given 


Chap.  VI. 


DIGESTION. 


Ill 


me  by  Prof.  Hoffmann.  For  comparison,  squares  of 
the  same  size  as  those  placed  on  the  leaves  were  left 
close  by  on  wet  moss.  These  soon  swelled,  but  re- 
tained their  angles  for  three  days;  after  five  days 
they  formed  rounded,  softened  masses,  but  even  on  the 
eighth  day  a trace  of  gelatine  could  still  be  detected. 
Other  squares  were  immersed  in  water,  and  these, 
though  much  swollen,  retained  their  angles  for  six 
days.  Squares  of  of  an  inch  (2*54  mm.),  just 
moistened  with  water,  were  placed  on  two  leaves  ; and 
after  two  or  three  days  nothing  was  left  on  them  but 
some  acid  viscid  fluid,  which  in  this  and  other  cases 
never  showed  any  tendency  to  regelatinise ; so  that 
the  secretion  must  act  on  the  gelatine  differently 
to  what  water  does,  and  apparently  in  the  same 
manner  as  gastric  juice.*  Four  squares  of  the  same 
size  as  before  were  then  soaked  for  three  days  in  water, 
and  placed  on  large  leaves ; the  gelatine  was  liquefied 
and  rendered  acid  in  two  days,  but  did  not  excite 
much  inflection.  The  leaves  began  to  re-expand  after 
four  or  five  days,  much  viscid  fluid  being  left  on  their 
discs,  as  if  but  little  had  been  absorbed.  One  of  these 
leaves,  as  soon  as  it  re-expanded,  caught  a small  fly, 
and  after  24  hrs.  was  closely  inflected,  showing  how 
much  more  potent  than  gelatine  is  the  animal  matter 
absorbed  from  an  insect.  Some  larger  pieces  of  gela- 
tine, soaked  for  five  days  in  water,  were  next  placed 
on  three  leaves,  but  these  did  not  become  much  in- 
flected until  the  third  day ; nor  was  the  gelatine 
completely  liquefied  until  the  fourth  day.  On  this 
day  one  leaf  began  to  re-expand ; the  second  on  the 
fifth ; and  third  on  the  sixth.  These  several  facts 


* Dr.  Lauder  Brunton,  ‘ Hand-  phys.  de  la  Digestion,’  1867,  p 

book  for  the  Phys.  Laboratory,’  249, 

1873,  pp.  477, 487 ; Schiff,  ‘ Lemons 

6 


112 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


prove  that  gelatine  is  far  from  acting  energetically 
on  Drosera. 

In  the  last  chapter  it  was  shown  that  a solution  of 
isinglass  of  commerce,  as  thick  as  milk  or  cream, 
induces  strong  inflection.  I therefore  wished  to  com- 
pare its  action  with  that  of  pure  gelatine.  Solutions 
of  one  part  of  both  substances  to  218  of  water  were 
made;  and  half-minim  drops  (*0296  ml.)  were  placed 
on  the  discs  of  eight  leaves,  so  that  each  received 
of  a grain,  or  *135  mg.  The  four  with  the  isin- 
glass were  much  more  strongly  inflected  than  the 
other  four.  I conclude  therefore  that  isinglass  con- 
tains some,  though  perhaps  very  little,  soluble  albu- 
minous matter.  As  soon  as  these  eight  leaves  re- 
expanded, they  were  given  bits  of  roast  meat,  and  in 
some  hours  all  became  greatly  inflected ; again  show- 
ing how  much  more  meat  excites  Drosera  than  does 
gelatine  or  isinglass.  This  is  an  interesting  fact,  as 
it  is  well  known  that  gelatine  by  itself  has  little 
power  of  nourishing  animals.* 

Ohondrin. — This  was  sent  me  by  Dr.  Moore  in  a 
gelatinous  state.  Some  was  slowly  dried,  and  a small 
chip  was  placed  on  a leaf,  and  a much  larger  chip  on 
a second  leaf.  The  first  was  liquefied  in  a day ; the 
larger  piece  was  much  swollen  and  softened,  but  was 
not  completely  liquefied  until  the  third  day.  The 
undried  jelly  was  next  tried,  and  as  a control  experi- 
ment small  cubes  were  left  in  water  for  four  days 
and  retained  their  angles.  Cubes  of  the  same  size 
were  placed  on  two  leaves,  and  larger  cubes  on  two 
other  leaves.  The  tentacles  and  laminae  of  the  latter 
were  closely  inflected  after  22  hrs.,  but  those  of  the 


* Dr.  Lauder  Brunton  gives  view  of  the  indirect  part  which 
in  the  ‘ Medical  Record,*  January  gelatine  plays  in  nutrition. 

1873,  p.  36,  an  account  ofVoit*s 


Chap.  VI. 


DIGESTION. 


113 


two  leaves  with  the  smaller  cubes  only  to  a moderate 
degree.  The  jelly  on  all  four  was  by  this  time  lique- 
fied, and  rendered  very  acid.  The  glands  were 
blackened  from  the  aggregation  of  their  protoplasmic 
contents.  In  46  hrs.  from  the  time  when  the  jelly 
was  given,  the  leaves  had  almost  re-expanded,  and 
completely  so  after  70  hrs. ; and  now  only  a little 
slightly  adhesive  fluid  was  left  unabsorbed  on  their 
discs. 

One  part  of  chondrin  jelly  was  dissolved  in  218 
parts  of  boiling  water,  and  half-minim  drops  were 
given  to  four  leaves  ; so  that  each  received  about 
of  a grain  (*135  mg.)  of  the  jelly ; and,  of  course, 
much  less  of  dry  chondrin.  This  acted  most  power- 
fully, for  after  only  3 hrs.  30  m.  all  four  leaves  were 
strongly  inflected.  Three  of  them  began  to  re- 
expand after  24  hrs.,  and  in  48  hrs.  were  completely 
open ; but  the  fourth  had  only  partially  re-expanded. 
All  the  liquefied  chondrin  was  by  this  time  absorbed. 
Hence  a solution  of  chondrin  seems  to  act  far  more 
quickly  and  energetically  than  pure  gelatine  or  isin- 
glass; but  I am  assured  by  good  authorities  that  it 
is  most  difficult,  or  impossible,  to  know  whether 
chondrin  is  pure,  and  if  it  contained  any  albumi- 
nous compound,  this  would  have  produced  the  above 
effects.  Nevertheless,  I have  thought  these  facts  worth 
giving,  as  there  is  so  much  doubt  on  the  nutritious 
value  of  gelatine ; and  Dr.  Lauder  Brunton  does  not 
know  of  any  experiments  with  respect  to  animals  on 
the  relative  value  of  gelatine  and  chondrin. 

Milk. — We  have  seen  in  the  last  chapter  that  milk 
acts  most  powerfully  on  the  leaves ; but  whether  this 
is  due  to  the  contained  casein  or  albumen,  I know  not. 
Rather  large  drops  of  milk  excite  so  much  secretion 
(which  is  very  acid)  that  it  sometimes  trickles  down 


114 


BROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


fioni  the  leaves,  and  this  is  likewise  characteristic  of 
chemically  prepared  casein.  Minute  drops  of  milk, 
placed  on  leaves,  were  coagulated  in  about  ten 
minutes.  Schiff  denies*  that  the  coagulation  of  milk 
by  gastric  juice  is  exclusively  due  to  the  acid  w^hich 
is  present,  but  attributes  it  in  part  to  the  pepsin; 
and  it  seems  doubtful  whether  with  Drosera  the 
coagulation  can  be  wholly  due  to  the  acid,  as  the 
secretion  does  not  commonly  colour  litmus  paper 
until  the  tentacles  have  become  well  inflected ; 
whereas  the  coagulation  commences,  as  we  have  seen, 
in  about  ten  minutes.  Minute  drops  of  skimmed 
milk  were  placed  on  the  discs  of  five  leaves;  and  a 
large  proportion  of  the  coagulated  matter  or  curd 
was  dissolved  in  6 hrs.  and  still  more  completely 
in  8 hrs.  These  leaves  re-expanded  after  two  days, 
and  the  viscid  fluid  left  on  their  discs  was  then  care- 
fully scraped  off  and  examined.  It  seemed  at  first 
sight  as  if  all  the  casein  had  not  been  dissolved,  for 
a little  matter  was  left  which  appeared  of  a whitish 
colour  by  reflected  light.  But  this  matter,  when 
examined  under  a high  power,  and  when  compared 
with  a minute  drop  of  skimmed  milk  coagulated  by 
acetic  acid,  was  seen  to  consist  exclusively  of  oil- 
globules,  more  or  less  aggregated  together,  with  no 
trace  of  casein.  As  I was  not  familiar  with  the 
microscopical  appearance  of  milk,  I asked  Dr.  Lauder 
Brunton  to  examine  the  slides,  and  he  tested  the 
globules  with  ether,  and  found  that  they  were  dis- 
solved. We  may,  therefore,  conclude  that  the  secretion 
quickly  dissolves  casein,  in  the  state  in  which  it  exists 
in  milk. 

Chemically  Prepared  Casein, — This  substance,  which 


♦ ‘Le9ons/  &c.  tom.  ii.  p.  151. 


Chap.  VI. 


DIGESTION. 


115 


is  insoluble  in  water,  is  supposed  by  many  chemists  to 
differ  from  the  casein  of  fresh  milk.  I procured  some, 
consisting  of  hard  globules,  from  Messrs.  Hopkins  and 
Williams,  and  tried  many  experiments  with  it.  Small 
particles  and  the  powder,  both  in  a dry  state  and 
moistened  with  water,  caused  the  leaves  on  which  they 
were  placed  to  be  inflected  very  slowly,  generally  not 
until  two  days  had  elapsed.  Other  particles,  wetted 
with  weak  hydrochloric  acid  (one  part  to  437  of 
water)  acted  in  a single  day,  as  did  some  casein 
freshly  prepared  for  me  by  Dr.  Moore.  The  ten- 
tacles commonly  remained  inflected  for  from  seven 
to  nine  days ; and  during  the  whole  of  this  time  the 
secretion  was  strongly  acid.  Even  on  the  eleventh 
day  some  secretion  left  on  the  disc  of  a fully  re- 
expanded leaf  was  strongly  acid.  The  acid  seems 
to  be  secreted  quickly,  for  in  one  case  the  secre- 
tion from  the  discal  glands,  on  which  a little 
powdered  casein  had  been  strewed,  coloured  litmus 
paper,  before  any  of  the  exterior  tentacles  were 
inflected. 

Small  cubes  of  hard  casein,  moistened  with  water, 
were  placed  on  two  leaves ; after  three  days  one  cube 
had  its  angles  a little  rounded,  and  after  seven  days 
both  consisted  of  rounded  softened  masses,  in  the 
midst  of  much  viscid  and  acid  secretion ; but  it  must 
not  be  inferred  from  this  fact  that  the  angles  were 
dissolved,  for  cubes  immersed  in  water  were  similarly 
acted  on.  After  nine  days  these  leaves  began  to  re- 
expand, but  in  this  and  other  cases  the  casein  did  not 
appear,  as  far  as  could  be  judged  by  the  eye,  much,  if 
at  all,  reduced  in  bulk.  According  to  Hoppe-Seyler 
and  Lubavin*  casein  consists  of  an  albuminous,  with 


♦ Dr.  Lauder  Bruntcn,  ‘ Handbook  for  Phys.  Lab.'  p.  529. 


116 


DKOSEKA  EOTUNDIFOLIA. 


Chap.  VI. 


a non-albuminous,  substance ; and  the  absorption  of  a 
very  small  quantity  of  the  former  would  excite  the 
leaves,  and  yet  not  decrease  the  casein  to  a percep- 
tible degree.  Schiff  asserts* — and  this  is  an  import- 
ant fact  for  us — that  ‘4a  caseine  purifiee  des  chimistes 
est  un  corps  presque  completement  inattaquable  par 
le  sue  gastrique.”  So  that  here  we  have  another 
point  of  accordance  between  the  secretion  of  Drosera 
and  gastric  juice,  as  both  act  so  diiBferently  on  the 
fresh  casein  of  milk,  and  on  that  prepared  by 
chemists. 

A few  trials  were  made  with  cheese ; cubes  of  of 
an  inch  (1*27  mm.)  were  placed  on  four  leaves,  and 
these  after  one  or  two  days  became  well  inflected, 
their  glands  pouring  forth  much  acid  secretion. 
After  five  days  they  began  to  re-expand,  but  one 
died,  and  some  of  the  glands  on  the  other  leaves  were 
injured.  Judging  by  the  eye,  the  softened  and  sub- 
sided masses  of  cheese,  left  on  the  discs,  were  very 
little  or  not  at  all  reduced  in  bulk.  We  may,  how- 
ever, infer  from  the  time  during  which  the  tentacles 
remained  inflected, — from  the  changed  colour  of  some 
of  the  glands, — and  from  the  injury  done  to  others, 
that  matter  had  been  absorbed  from  the  cheese. 

Legumin. — I did  not  procure  this  substance  in  a 
separate  state ; but  there  can  hardly  be  a doubt  that 
it  would  be  easily  digested,  judging  from  the  powerful 
efi‘ect  produced  by  drops  of  a decoction  of  green 
peas,  as  described  in  the  last  chapter.  Thin  slices  of 
a dried  pea,  after  being  soaked  in  water,  were  placed 
on  two  leaves ; these  became  somewhat  inflected  in 
the  course  of  a single  hour,  and  most  strongly  so  in 
21  hrs.  They  re-expanded  after  three  or  four  days, 


* * Lemons,’  &c.  tom.  ii.  p.  153. 


Chap.  VI. 


DIGESTION. 


117 


The  slices  were  not  liquefied,  for  the  walls  of  the  cells, 
composed  of  cellulose,  are  not  in  the  least  acted  on 
by  the  secretion. 

Pollen. — A little  fresh  pollen  from  the  common  pea 
was  placed  on  the  discs  of  five  leaves,  which  soon 
became  closely  inflected,  and  remained  so  for  two  or 
three  days. 

The  grains  being  then  removed,  and  examined  under 
the  microscope,  were  found  discoloured,  with  the  oil- 
globules  remarkably  aggregated.  Many  had  their 
contents  much  shrunk,  and  some  were  almost  empty. 
In  only  a few  cases  were  the  pollen-tubes  emitted. 
There  could  be  no  doubt  that  the  secretion  had 
penetrated  the  outer  coats  of  the  grains,  and  had 
partially  digested  their  contents.  So  it  must  be 
with  the  gastric  juice  of  the  insects  which  feed  on 
pollen,  without  masticating  it."^  Drosera  in  a state  of 
nature  cannot  fail  to  profit  to  a certain  extent  by  this 
power  of  digesting  pollen,  as  innumerable  grains  from 
the  carices,  grasses,  rumices,  fir-trees,  and  other  wind- 
fertilised  plants,  which  commonly  grow  in  the  same 
neighbourhood,  will  be  inevitably  caught  by  the  viscid 
secretion  surrounding  the  many  glands. 

Gluten. — This  substance  is  composed  of  two  albu- 
minoids, one  soluble,  the  other  insoluble  in  alcohol.f 
Some  was  prepared  by  merely  washing  wheaten  flour 
in  water.  A provisional  trial  was  made  with  rather 
large  pieces  placed  on  two  leaves ; these,  after  21  hrs., 
were  closely  inflected,  and  remained  so  for  four  days, 
when  one  was  killed  and  the  other  had  its  glands 
extremely  blackened,  but  was  not  afterwards  observed. 


* Mr.  A.  W.  Bennett  found  the  Hort.  Soc.  of  London,’  vol.  iv, 
undigested  coats  of  the  grains  in  1874,  p.  158. 
the^  intestinal  canal  of  pollen-  f Watts’  ‘ Diet,  of  Chemistry, 
eating  Diptera ; see  ‘ Journal  of  vol.  ii.  1872,  p.  873. 


118 


DROSERA  ROTUNDIFOLIA. 


Chap.  YI. 


Smaller  bits  were  placed  on  two  leaves;  these  were 
only  slightly  inflected  in  two  days,  but  afterwards 
became  much  more  so.  Their  secretion  was  not  so 
strongly  acid  as  that  of  leaves  excited  by  casein. 
The  bits  of  gluten,  after  lying  for  three  days  on  the 
leaves,  were  more  transparent  than  other  bits  left  for 
the  same  time  in  water.  After  seven  days  both  leaves 
re-expanded,  but  the  gluten  seemed  hardly  at  all 
reduced  in  bulk.  The  glands  which  had  been  in 
contact  with  it  were  extremely  black.  Still  smaller 
bits  of  half  putrid  gluten  were  now  tried  on  two 
leaves;  these  were  well  inflected  in  24  hrs.,  and 
thoroughly  in  four  days,  the  glands  in  contact  being 
much  blackened.  After  five  days  one  leaf  began  to 
re-expand,  and  after  eight  days  both  were  fully  re- 
expanded, some  gluten  being  still  left  on  their  discs. 
Four  little  chips  of  dried  gluten,  just  dipped  in 
water,  were  next  tried,  and  these  acted  rather  dif- 
ferently from  fresh  gluten.  One  leaf  was  almost 
fully  re-expanded  in  three  days,  and  the  other  three 
leaves  in  four  days.  The  chips  were  greatly  softened, 
almost  liquefied,  but  not  nearly  all  dissolved.  The 
glands  which  had  been  in  contact  with  them,  instead 
of  being  much  blackened,  were  of  a very  pale  colour, 
and  many  of  them  were  evidently  killed. 

In  not  one  of  these  ten  cases  was  the  whole  of  the 
gluten  dissolved,  even  when  very  small  bits  were 
given.  I therefore  asked  Dr.  Burden  Sanderson  to 
try  gluten  in  artificial  digestive  fluid  of  pepsin  with 
hydrochloric  acid ; and  this  dissolved  the  whole. 
The  gluten,  however,  was  acted  on  much  more  slowly 
than  fibrin ; the  proportion  dissolved  within  four 
hours  being  as  40*8  of  gluten  to  100  of  fibrin. 
Gluten  was  also  tried  in  two  other  digestive  fluids, 
in  which  hydrochloric  acid  was  replaced  by  propionic 


Chap.  VI. 


DIGESTION. 


119 


and  butyric  acids,  and  it  was  completely  dissolved  by 
these  fluids  at  the  ordinary  temperature  of  a room. 
Here,  then,  at  last,  we  have  a case  in  which  it  appears 
that  there  exists  an  essential  difference  in  digestive 
power  between  the  secretion  of  Drosera  and  gastric 
juice;  the  difference  being  confined  to  the  ferment, 
for,  as  we  have  just  seen,  pepsin  in  combination  with 
acids  of  the  acetic  series  acts  perfectly  on  gluten. 
I believe  that  the  explanation  lies  simply  in  the  fact 
that  gluten  is  too  powerful  a stimulant  (like  raw 
meat,  or  phosphate  of  lime,  or  even  too  large  a piece 
of  albumen),  and  that  it  injures  or  kills  the  glands 
before  they  have  had  time  to  pour  forth  a sufficient 
supply  of  the  proper  secretion.  That  some  matter  is 
absorbed  from  the  gluten,  we  have  clear  evidence  in 
the  length  of  time  during  which  the  tentacles  remain 
inflected,  and  in  the  greatly  changed  colour  of  the 
glands. 

At  the  suggestion  of  Dr.  Sanderson,  some  gluten 
was  left  for  15  hrs.  in  weak  hydrochloric  acid  (-02  per 
cent.),  in  order  to  remove  the  starch.  It  became 
colourless,  more  transparent,  and  swollen.  Small 
portions  were  washed  and  placed  on  five  leaves,  which 
were  soon  closely  inflected,  but  to  my  surprise  re- 
expanded completely  in  48  hrs.  A mere  vestige  of 
gluten  was  left  on  two  of  the  leaves,  and  not  a vestige 
on  the  other  three.  The  viscid  and  acid  secretion, 
which  remained  on  the  discs  of  the  three  latter 
leaves,  was  scraped  off  and  examined  by  my  son 
under  a high  power ; but  nothing  could  be  seen 
except  a little  dirt,  and  a good  many  starch  grains 
which  had  not  been  dissolved  by  the  hydrochloric 
acid.  Some  of  the  glands  were  rather  pale.  We 
thus  learn  that  gluten,  treated  with  weak  hydro- 
chloric acid,  is  not  so  powerful  or  so  enduring  a 


120 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


stimulant  as  fresh  gluten,  and  does  not  much  injure 
the  glands ; and  we  further  learn  that  it  can  be  di- 
gested quickly  and  completely  by  the  secretion. 

Globulin  or  Crystallin, — This  substance  was  kindly  prepared 
for  me  from  the  lens  of  the  eye  by  Dr.  Moore,  and  consisted  of 
hard,  colourless,  transparent  fragments.  It  is  said*  that  globulin 
ought  to  ""swell  up  in  water  and  dissolve,  for  the  most  part 
forming  a gummy  liquid but  this  did  not  occur  with  the  above 
fragments,  though  kept  in  water  for  four  days.  Particles,  some 
moistened  with  water,  others  with  weak  hydrochloric  acid, 
others  soaked  in  water  for  one  or  two  days,  were  placed  on 
nineteen  leaves.  Most  of  these  leaves,  especially  those  with  the 
long  soaked  particles,  became  strongly  inflected  in  a few  hours. 
The  greater  number  re-expanded  after  three  or  four  days ; but 
three  of  the  leaves  remained  inflected  during  one,  two,  or  three 
additional  days.  Hence  some  exciting  matter  must  have  been 
absorbed;  but  the  fragments,  though  perhaps  softened  in  a 
greater  degree  than  those  kept  for  the  same  time  in  water, 
retained  all  their  angles  as  sharp  as  ever.  As  globulin  is  an 
albuminous  substance,  I was  astonished  at  this  result ; and  my 
object  being  to  compare  the  action  of  the  secretion  with  that  ot 
gastric  juice,  I asked  Dr.  Burdon  Sanderson  to  try  some  of  the 
globulin  used  by  me.  He  reports  that  ""  it  was  subjected  to  a 
liquid  containing  per  cent,  of  hydrochloric  acid,  and  about 
1 per  cent,  of  glycerine  extract  of  the  stomach  of  a dog.  It  was 
then  ascertained  that  this  liquid  was  capable  of  digesting  1*31 
of  its  weight  of  unboiled  fibrin  in  1 hr.;  whereas,  during  the 
hour,  only  0*141  of  the  above  globulin  was  dissolved.  In  both 
cases  an  excess  of  the  substance  to  be  digested  was  subjected  to 
the  liquid.”!  We  thus  see  that  within  the  same  time  less  than 
one-ninth  by  weight  of  globulin  than  of  fibrin  was  dissolved  ; 
and  bearing  in  mind  that  pepsin  with  acids  of  the  acetic  series 
has  only  about  one-third  of  the  digestive  power  of  j^epsin  with 
hydrochloric  acid,  it  is  not  surprising  that  the  fragments  of 


* Watts’  ‘ Diet,  of  Chemistry,’ 
vol.  ii.  p.  874. 

t I may  add  that  Dr.  Sander- 
son prepared  some  fresh  globulin 
by  Schmidt’s  method,  and  of  this 
0*865  was  dissolved  within  the 
same  time,  namely,  one  hour ; so 


that  it  was  far  more  soluble  than 
that  which  I used,  though  less 
soluble  than  fibrin,  of  which,  as 
we  have  seen,  1*31  was  dissolved. 
I wish  that  I had  tried  on  Dro- 
sera  globulin  prepared  by  thif 
method. 


OUAP.  VI. 


DIGESTION. 


121 


globulin  were  not  corroded  or  rounded  by  the  secretion  of 
Drosera,  though  some  soluble  matter  was  certainly  extracted 
from  them  and  absorbed  by  the  glands. 

Hcematin. — Some  dark  red  granules,  prepared  from  bullock’s 
blood,  were  given  me ; these  were  found  by  Dr.  Sanderson  to 
be  insoluble  in  water,  acids,  and  alcohol,  so  that  they  were  pro- 
bably hsematin,  together  with  other  bodies  derived  from  the 
blood.  Particles  with  little  drops  of  water  were  placed  on 
four  leaves,  three  of  which  were  pretty  closely  inflected  in  two 
days ; the  fourth  only  moderately  so.  On  the  third  day  the 
glands  in  contact  with  the  hsematin  were  blackened,  and  some 
of  the  tentacles  seemed  injured.  After  five  days  two  leaves 
died,  and  the  third  was  dying ; the  fourth  was  beginning  to  re- 
expand, but  many  of  its  glands  were  blackened  and  injured. 
It  is  therefore  clear  that  matter  had  been  absorbed  which  was 
either  actually  poisonous  or  of  too  stimulating  a nature.  The 
particles  were  much  more  softened  than  those  kept  for  the  same 
time  in  water,  but,  judging  by  the  eye,  very  little  reduced  in 
bulk.  Dr.  Sanderson  tried  this  substance  with  artificial  digestive 
fluid,  in  the  manner  described  under  globulin,  and  found  that 
whilst  1*31  of  fibrin,  only  0*456  of  the  haematin  was  dissolved 
in  an  hour ; but  the  dissolution  by  the  secretion  of  even  a less 
amount  would  account  for  its  action  on  Drosera.  The  residue 
left  by  the  artificial  digestive  fluid  at  first  yielded  nothing  more 
to  it  during  several  succeeding  days. 

Substances  which  are  not  Digested  by  the  Secretion. 

All  the  substances  hitherto  mentioned  cause  pro- 
longed inflection  of  the  tentacles,  and  are  either  com- 
pletely or  at  least  partially  dissolved  by  the  secretion. 
But  there  are  many  other  substances,  some  of  them 
containing  nitrogen,  which  are  not  in  the  least  acted 
on  by  the  secretion,  and  do  not  induce  inflection  for  a 
longer  time  than  do  inorganic  and  insoluble  objects. 

V These  unexciting  and  indigestible  substances  are,  as 
far  as  I have  observed,  epidermic  productions  (such 
as  bits  of  human  nails,  balls  of  hair,  the  quills  of 
feathers),  fibro-elastic  tissue,  mucin,  pepsin,  urea, 
chitine,  chlorophyll,  cellulose,  gun-cotton,  fat,  oil,  and 
starch.  \ 


122 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


To  these  may  be  added  dissolved  sugar  and  gum, 
diluted  alcohol,  and  vegetable  infusions  not  containing 
albumen,  for  none  of  these,  as  shown  in  the  last 
chapter,  excite  inflection.  Now,  it  is  a remarkable 
fact,  which  affords  additional  and  important  evidence, 
that  the  ferment  of  Drosera  is  closely  similar  to  or 
identical  with  pepsin,  that  none  of  these  same  sub- 
stances are,  as  far  as  it  is  known,  digested  by  the  gas- 
tric juice  of  animals,  though  some  of  them  are  acted 
on  by  the  other  secretions  of  the  alimentary  canal. 
Nothing  more  need  be  said  about  some  of  the  above 
enumerated  substances,  excepting  that  they  were  re- 
peatedly tried  on  the  leaves  of  Drosera,  and  were  not 
in  the  least  affected  by  the  secretion.  About  the 
others  it  will  be  advisable  to  give  my  experiments. 

Fibro-elasflc  Tissue. — We  have  already  seen  that  when  little 
cubes  of  meat,  &c.,  were  placed  on  leaves,  the  muscles,  areolar 
tissue,  and  cartilage  were  completely  dissolved,  but  the  fibro- 
elastic  tissue,  even  the  most  delicate  threads,  were  left  without 
the  least  signs  of  having  been  attacked.  And  it  is  well  known 
that  this  tissue  cannot  be  digested  by  the  gastric  juice  of 
animals.* 

Mucin. — As  this  substance  contains  about  7 per  cent,  of 
nitrogen,  I expected  that  it  would  have  excited  the  leaves 
greatly  and  been  digested  by  the  secretion,  but  in  this  I 
was  mistaken.  From  what  is  stated  in  chemical  works,  it 
appears  extremely  doubtful  whether  mucin  can  be  prepared  as 
a pure  principle.  That  which  I used  (prepared  by  Dr.  Moore) 
was  dry  and  hard.  Particles  moistened  with  water  were  placed 
on  four  leaves,  but  after  two  days  there  was  only  a trace  of 
inflection  in  the  immediately  adjoining  tentacles.  These  leaves 
were  then  tried  with  bits  of  meat,  and  all  four  soon  became 
strongly  inflected.  Some  of  the  dried  mucin  was  then  soaked 
in  water  for  two  days,  and  little  cubes  of  the  proper  size 
were  placed  on  three  leaves.  After  four  days  the  tentacles 


* See,  for  instance,  Schiff,  ‘Phys.  de  Ja  Digestion,’  1867.  tom.  ii 
p.  38. 


C/HAP.  YI. 


DIGESTION. 


123 


round  the  margins  of  the  discs  were  a little  inflected,  and 
the  secretion  collected  on  the  disc  was  acid,  but  the  exterior 
tentacles  were  not  affected.  One  leaf  began  to  re-expand  on  the 
fourth  day,  and  all  were  fully  re-expanded  on  the  sixth.  The 
glands  which  had  been  in  contact  with  the  mucin  were  a little 
darkened.  We  may  therefore  conclude  that  a small  amount  of 
some  impurity  of  a moderately  exciting  nature  had  been 
absorbed.  That  the  mucin  employed  by  me  did  contain  some 
soluble  matter  was  proved  by  Dr.  Sanderson,  who  on  subjecting 
it  to  artificial  gastric  juice  found  that  in  1 hr.  some  was  dis- 
solved, but  only  in  the  proportion  of  23  to  100  of  fibrin  during 
the  same  time.  The  cubes,  though  perhaps  rather  softer  than 
those  left  in  water  for  the  same  time,  retained  their  angles  as 
sharp  as  ever.  We  may  therefore  infer  that  the  mucin  itself 
was  not  dissolved  or  digested.  Nor  is  it  digested  by  the 
gastric  juice  of  living  animals,  and  according  to  Schiff*  it  is  a 
layer  of  this  substance  which  protects  the  coats  of  the  stomach 
from  being  corroded  during  digestion. 

Pepsin, — My  experiments  are  hardly  worth  giving,  as  it  is 
scarcely  possible  to  prepare  pepsin  free  from  other  albuminoids ; 
but  I was  curious  to  ascertain,  as  far  as  that  was  possible, 
whether  the  ferment  of  the  secretion  of  Drosera  would  act  on 
the  ferment  of  the  gastric  juice  of  animals.  I first  used  the 
common  pepsin  sold  for  medicinal  purposes,  and  afterwards 
some  which  was  much  purer,  prepared  for  me  by  Dr.  Moore. 
Five  leaves  to  which  a considerable  quantity  of  the  former  was 
given  remained  inflected  for  five  days ; four  of  them  then  died, 
apparently  from  too  great  stimulation.  I then  tried  Dr.  Moore’s 
pepsin,  making  it  into  a paste  with  water,  and  placing  such 
small  particles  on  the  discs  of  five  leaves  that  all  would  have 
been  quickly  dissolved  had  it  been  meat  or  albumen.  The 
leaves  were  soon  inflected;  two  of  them  began  to  re-expand 
after  only  20  hrs.,  and  the  other  three  were  almost  completely 
re-expanded  after  44  hrs.  Some  of  the  glands  which  had  been 
in  contact  with  the  particles  of  pepsin,  or  with  the  acid  secre- 
tion surrounding  them,  were  singularly  pale,  whereas  others 
were  singularly  dark-coloured.  Some  of  the  secretion  was 
scraped  off  and  examined  under  a high  power;  and  it  abounded 
with  granules  undistinguishable  from  those  of  pepsin  left  in 
water  for  the  same  length  of  time.  We  may  therefore  infer, 
as  highly  probable  (remembering  what  small  quantities  were 
given),  that  the  ferment  of  Drosera  does  not  act  on  or  digest 


* ‘ Lemons  phys.  de  la  Digestion/  1867,  tom.  ii.  p.  304. 


124 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


pepsin,  but  absorbs  from  it  some  albuminous  impurity  which 
induces  inflection,  and  which  in  large  quantity  is  highly 
injurious.  Dr.  Lauder  Brunton  at  my  request  endeavoured  to 
ascertain  whether  pepsin  with  hydrochloric  acid  would  digest 
pepsin,  and  as  far  as  he  could  judge,  it  had  no  such  power. 
Gastric  juice,  therefore,  apparently  agrees  in  this  respect  with 
the  secretion  of  Drosera. 

Urea. — It  seemed  to  me  an  interesting  inquiry  whether  this 
refuse  of  the  living  body,  which  contains  much  nitrogen, 
would,  like  so  many  other  animal  fluids  and  substances,  be 
absorbed  by  the  glands  of  Drosera  and  cause  inflection.  Half- 
minim drops  of  a solution  of  one  part  to  437  of  water  were 
placed  on  the  discs  of  four  leaves,  each  drop  containing  the 
quantity  usually  employed  by  me,  namely  of  a grain,  or 
•0674  mg.;  but  the  leaves  were  Wdly  at  all  affected.  They 
were  then  tested  with  bits  of  meat,  and  soon  became  closely 
inflected.  I repeated  the  same  experiment  on  four  leaves 
with  some  fresh  urea  prepared  by  Dr.  Moore;  after  two  days 
there  was  no  inflection;  I then  gave  them  another  dose,  but 
still  there  was  no  inflection.  These  leaves  were  afterwards 
tested  with  similarly  sized  drops  of  an  infusion  of  raw  meat, 
and  in  6 hrs.  there  was  considerable  inflection,  which  became 
excessive  in  24  hrs.  But  the  urea  apparently  was  not  quite 
pure,  for  when  four  leaves  were  immersed  in  2 dr.  (7*1  ml.)  of 
the  solution,  so  that  all  the  glands,  instead  of  merely  those  on 
the  disc,  were  enabled  to  absorb  any  small  amount  of  impurity 
in  solution,  there  was  considerable  inflection  after  24  hrs., 
certainly  more  than  would  have  followed  from  a similar  im- 
mersion in  pure  water.  That  the  urea,  which  was  not  per- 
fectly white,  should  have  contained  a sufficient  quantity  of 
albuminous  matter,  or  of  some  salt  of  ammonia,  to  have  caused 
the  above  effect,  is  far  from  surprising,  for,  as  we  shall  see 
in  the  next  chapter,  astonishingly  small  doses  of  ammonia 
are  highly  efficient.  We  may  therefore  conclude  that  urea  itself 
is  not  exciting  or  nutritious  to  Drosera ; nor  is  it  modified  by 
the  secretion,  so  as  to  be  rendered  nutritious,  for,  had  this  been 
the  case,  all  the  leaves  with  drops  on  their  discs  assuredly 
would  have  been  well  inflected.  Dr.  Lauder  Brunton  informs 
me  that  from  experiments  made  at  my  request  at  St.  Bartho- 
lomew’s Hospital  it  appears  that  urea  is  not  acted  on  by 
artificial  gastric  juice,  that  is  by  pepsin  with  hydrochloric  acid. 

Chitine. — The  chitinous  coats  of  insects  naturally  captured  by 
the  leaves  do  not  appear  in  the  least  corroded.  Small  square 
pieces  of  the  delicate  wing  and  of  the  elytron  of  a Staphylinus 


Chap.  VI. 


DIGESTION. 


125 


were  placed  on  some  leaves,  and  after  these  had  re-expanded, 
the  pieces  were  carefully  examined.  Their  angles  were  as 
sharp  as  ever,  and  they  did  not  differ  in  appearance  from  the 
other  wing  and  elytron  of  the  same  insect  which  had  been  left 
in  water.  The  elytron,  however,  had  evidently  yielded  some 
nutritious  matter,  for  the  leaf  remained  clasped  over  it  for  four 
days ; whereas  the  leaves  with  bits  of  the  true  wing  re-expanded 
on  the  second  day.  Any  one  who  will  examine  the  excrement 
of  insect-eating  animals  will  see  how  powerless  their  gastric 
juice  is  on  chitine. 

Cellulose. — I did  not  obtain  this  substance  in  a separate  state, 
but  tried  angular  bits  of  dry  wood,  cork,  sphagnum  moss,  linen, 
and  cotton  thread.  None  of  these  bodies  were  in  the  least 
attacked  by  the  secretion,  and  they  caused  only  that  moderate 
amount  of  inflection  which  is  common  to  all  inorganic  objects. 
Gun-cotton,  which  consists  of  cellulose,  with  the  hydrogen 
replaced  by  nitrogen,  was  tried  with  the  same  result.  We  have 
seen  that  a decoction  of  cabbage-leaves  excites  the  most  power- 
ful inflection.  I therefore  placed  two  little  square  bits  of  the 
blade  of  a cabbage-leaf,  and  four  little  cubes  cut  from  the 
midrib,  on  six  leaves  of  Drosera.  These  became  well  inflected 
in  12  hrs.,  and  remained  so  for  between  two  and  four  days; 
the  bits  of  cabbage  being  bathed  all  the  time  by  acid  secre- 
tion. This  shows  that  some  exciting  matter,  to  which  I shall 
presently  refer,  had  been  absorbed ; but  the  angles  of  the 
squares  and  cubes  remained  as  sharp  as  ever,  proving  that  the 
framework  of  cellulose  had  not  been  attacked.  Small  square 
bits  of  spinach-leaves  were  tried  with  the  same  result;  the 
glands  pouring  forth  a moderate  supply  of  acid  secretion, 
and  the  tentacles  remaining  inflected  for  three  days.  We  have 
also  seen  that  the  delicate  coats  of  pollen  grains  are  not  dissolved 
by  the  secretion.  It  is  well  known  that  the  gastric  juice  of 
animals  does  not  attack  cellulose. 

. Chlo'rophyll. — This  substance  was  tried,  as  it  contains  nitrogen. 
Dr.  Moore  sent  me  some  preserved  in  alcohol;  it  was  dried,  but 
soon  deliquesced.  Particles  were  placed  on  four  leaves;  after 
3 hrs.  the  secretion  was  acid ; after  8 hrs.  there  was  a good  deal 
of  inflection,  which  in  24  hrs.  became  fairly  well  marked.  After 
four  days  two  of  the  leaves  began  to  open,  and  the  other  two 
were  then  almost  fully  re-expanded.  It  is  therefore  clear  that 
this  chlorophyll  contained  matter  which  excited  the  leaves  to  a 
moderate  degree ; but  judging  by  the  eye,  little  or  none  was  dis- 
solved ; so  that  in  a pure  state  it  would  not  probably  have  been 
attacked  by  the  secretion.  Dr.  Sanderson  tried  that  which  I 


126 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


used,  as  well  as  some  freshly  prepared,  with  artificial  digestive 
liquid,  and  found  tha^  it  was  not  digested.  Dr.  Lauder  Brunton 
likewise  tried  some  prepared  by  the  process  given  in  the  British 
Pharmacopoeia,  and  exposed  it  for  five  days  at  the  temperature 
of  37°  Cent,  to  digestive  liquid,  but  it  was  not  diminished  in 
bulk,  though  the  fluid  acquired  a slightly  brown  colour.  It  was 
also  tried  with  the  glycerine  extract  of  pancreas  with  a negative 
result.  Nor  does  chlorophyll  seem  affected  by  the  intestinal 
secretions  of  various  animals,  judging  by  the  colour  of  their 
excrement. 

It  must  not  be  supposed  from  these  facts  that  the  grains  of 
chlorophyll,  as  they  exist  in  living  plants,  cannot  be  attacked  by 
the  secretion;  for  these  grains  consist  of  protoplasm  merely 
coloured  by  chlorophyll.  My  son  Prancis  placed  a thin  shce  of 
spinach  leaf,  moistened  with  saliva,  on  a leaf  of  Drosera,  and 
other  slices  on  damp  cotton-wool,  all  exposed  to  the  same 
temperature.  After  19  hrs.  the  slice  on  the  leaf  of  Drosera  was 
bathed  in  much  secretion  from  the  inflected  tentacles,  and  was 
now  examined  under  the  microscope.  No  perfect  grains  of 
chlorophyll  could  be  distinguished ; some  were  shrunken,  of  a 
yellowish-green  colour,  and  collected  in  the  middle  of  the  cells ; 
others  were  disintegrated  and  formed  a yellowish  mass,  likewise 
in  the  middle  of  the  cells.  On  the  other  hand,  in  the  slices 
surrounded  by  damp  cotton-wool,  the  grains  of  chlorophyll  were 
green  and  as  perfect  as  ever.  My  son  also  placed  some  slices 
in  artificial  gastric  juice,  and  these  were  acted  on  in  nearly  the 
same  manner  as  by  the  secretion.  We  have  seen  that  bits  of 
fresh  cabbage  and  spinach  leaves  cause  the  tentacles  to  be  in- 
flected and  the  glands  to  pour  forth  much  acid  secretion ; and 
there  can  be  little  doubt  that  it  is  the  protoplasm  forming  the 
grains  of  chlorophyll,  as  well  as  that  lining  the  walls  of  the 
cells,  which  excites  the  leaves. 

Fat  and  Oil, — Cubes  of  almost  pure  uncooked  fat,  placed  on 
several  leaves,  did  not  have  their  angles  in  the  least  rounded. 
We  have  also  seen  that  the  oil-globules  in  milk  are  not  digested. 
Nor  does  olive  oil  dropped  on  the  discs  of  leaves  cause  any 
inflection ; but  when  they  are  immersed  in  olive  oil,  they  become 
strongly  inflected;  but  to  this  subject  I shall  have  to  recur. 
Oily  substances  are  not  digested  by  the  gastric  juice  of  animals. 

Starch, — Rather  large  bits  of  dry  starch  caused  well-marked 
inflection,  and  the  leaves  did  not  re-expand  until  the  fourth 
day ; but  I have  no  doubt  that  this  was  due  to  the  prolonged 
irritation  of  the  glands,  as  the  starch  continued  to  absorb  the 
secretion.  The  particles  were  not  in  the  least  reduced  in  size ; 


Chap.  YI. 


DIGESTION. 


127 


and  we  know  that  leaves  immersed  in  an  emulsion  of  starch 
are  not  at  all  affected.  I need  hardly  say  that  starch  is  not 
digested  by  the  gastric  juice  of  animals. 

Action  of  the  Secretion  on  Living  Seeds, 

The  results  of  some  experiments  on  living  seeds,  selected  by 
hazard,  may  here  be  given,  though  they  bear  only  indirectly  on 
our  present  subject  of  digestion. 

Seven  cabbage  seeds  of  the  previous  year  were  placed  on  the 
same  number  of  leaves.  Some  of  these  leaves  were  moderately, 
but  the  greater  number  only  slightly  inflected,  and  most  of 
them  re-expanded  on  the  third  day.  One,  however,  remained 
clasped  till  the  fourth,  and  another  till  the  flfth  day.  These 
leaves  therefore  were  excited  somewhat  more  by  the  seeds  than 
by  inorganic  objects  of  the  same  size.  After  they  re-expanded, 
the  seeds  were  placed  under  favourable  conditions  on  damp 
sand ; other  seeds  of  the  same  lot  being  tried  at  the  same  time 
in  the  same  manner,  and  found  to  germinate  well.  Of  the  seven 
seeds  which  had  been  exposed  to  the  secretion,  only  three  ger- 
minated ; and  one  of  the  three  seedlings  soon  perished,  the  tip 
of  its  radicle  being  from  the  first  decayed,  and  the  edges  of 
its  cotyledons  of  a dark  brown  colour;  so  that  altogether  five 
out  of  the  seven  seeds  ultimately  perished. 

Eadish  seeds  {Raphanus  sativus)  of  the  previous  year  were 
placed  on  three  leaves,  which  became  moderately  inflected,  and 
re-expanded  on  the  third  or  fourth  day.  Two  of  these  seeds 
were  transferred  to  damp  sand ; only  one  germinated,  and  that 
very  slowly.  This  seedling  had  an  extremely  short,  crooked, 
diseased,  radicle,  with  no  absorbent  hairs ; and  the  cotyledons 
were  oddly  mottled  with  purple,  with  the  edges  blackened  and 
partly  withered. 

Cress  seeds  (Lepidum  sativum)  of  the  previous  year  were 
placed  on  four  leaves ; two  of  these  next  morning  were  mode- 
rately and  two  strongly  inflected,  and  remained  so  for  four, 
five,  and  even  six  days.  Soon  after  these  seeds  were  placed  on 
the  leaves  and  had  become  damp,  they  secreted  in  the  usual 
manner  a layer  of  tenacious  mucus ; and  to  ascertain  whether 
it  was  the  absorption  of  this  substance  by  the  glands  which 
caused  so  much  inflection,  two  seeds  were  put  into  water,  and 
as  much  of  the  mucus  as  possible  scraped  off.  They  were  then 
placed  on  leaves,  which  became  very  strongly  inflected  in  the 
course  of  3 hrs.,  and  were  still  closely  inflected  on  the  third 
day ; so  that  it  evidently  was  not  the  mucus  which  excited  so 


128 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


much  inflection ; on  the  contrary,  this  served  to  a certain  extent 
as  a protection  to  the  seeds.  Two  of  the  six  seeds  germinated 
whilst  still  lying  on  the  leaves,  but  the  seedlings,  when  trans- 
ferred to  damp  sand,  soon  died ; of  the  other  four  seeds,  only  one 
germinated. 

Two  seeds  of  mustard  {Sinapis  nigra),  two  of  celery  {Apium 
graveolens) — ^both  of  the  previous  year,  two  seeds  well  soaked  of 
caraway  {Carum  carui),  and  two  of  wheat,  did  not  excite  the 
leaves  more  than  inorganic  objects  often  do.  Five  seeds,  hardly 
ripe,  of  a buttercup  (Ranunculus),  and  two  fresh  seeds  of  Ane- 
mone nemorosa,  induced  only  a little  more  effect.  On  the  other 
hand,  four  seeds,  perhaps  not  quite  ripe,  of  Carex  sylvatica  caused 
the  leaves  on  which  they  were  placed  to  be  very  strongly  in- 
flected ; and  these  only  began  to  re-expand  on  the  third  day, 
one  remaining  inflected  for  seven  days. 

It  follows  from  these  few  facts  that  different  kinds  of  seeds 
excite  the  leaves  in  very  different  degrees;  whether  this  is 
solely  due  to  the  nature  of  their  coats  is  not  clear.  In  the  case 
of  the  cress  seeds,  the  partial  removal  of  the  layer  of  mucus 
hastened  the  inflection  of  the  tentacles.  Whenever  the  leaves 
remain  inflected  during  several  days  over  seeds,  it  is  clear  that 
they  absorb  some  matter  from  them.  That  the  secretion  pene- 
trates their  coats  is  also  evident  from  the  large  proportion  of 
cabbage,  raddish,  and  cress  seeds  which  were  killed,  and  from 
several  of  the  seedlings  being  greatly  injured.  This  injury  to 
the  seeds  and  seedlings  may,  however,  be  due  solely  to  the  acid 
of  the  secretion,  and  not  to  any  process  of  digestion ; for  Mr. 
Traherne  Moggridge  has  shown  that  very  weak  acids  of  the 
acetic  series  are  highly  injurious  to  seeds.  It  never  occurred 
to  me  to  observe  whether  seeds  are  often  blown  on  to  the  viscid 
leaves  of  plants  growing  in  a state  of  nature;  but  this  can 
hardly  fail  sometimes  to  occur,  as  we  shall  hereafter  see  in  the 
case  of  Pinguicula.  If  so,  Drosera  wiU  profit  to  a slight  degree 
by  absorbing  matter  from  such  seeds. 


Summary  and  Concluding  Remarks  on  the  Digestive 
Power  of  Drosera. 

i 

When  the  glands  on  the  disc  are  excited  either 
by  the  absorption  of  nitrogenous  matter  or  by 
mechanical  irritation,  their  secretion  increases  in 
quantity  and  becomes  acid.  They  likewise  transmit 


Chap.  VI. 


DIGESTION. 


129 


some  influence  to  the  glands  of  the  exterior  ten- 
tacles, causing  them  to  secrete  more  copiously;  and 
their  secretion  likewise  becomes  acid.  With  ani- 
mals, according  to  Schiff,*  mechanical  irritation  ex- 
cites the  glands  of  the  stomach  to  secrete  an  acid, 
but  not  pepsin.  Now,  I have  every  reason  to  be- 
lieve (though  the  fact  is  not  fully  established),  that 
although  the  glands  of  Drosera  are  continually  secret- 
ing viscid  fluid  to  replace  that  lost  by  evaporation, 
yet  they  do  not  secrete  the  ferment  proper  for  di- 
gestion when  mechanically  irritated,  but  only  after 
absorbing  certain  matter,  probably  of  a nitrogenous 
nature.A  I infer  that  this  is  the  case,  as  the  secretion 
from  a large  number  of  leaves  which  had  been 
irritated  by  particles  of  glass  placed  on  their  discs 
did  not  digest  albumen;  and  more  especially  from 
the  analogy  of  Dionaea  and  Nepenthes.  In  like 
manner,  the  glands  of  the  stomach  of  animals  secrete 
pepsin,  as  Schiflf  asserts,  only  after  they  have  ab- 
sorbed certain  soluble  substances,  which  he  desig- 
nates as  peptogenes.  Inhere  is,  therefore,  a remarkable 
parallelism  between  the  glands  of  Drosera  and  those 
of  the  stomach  in  the  secretion  of  their  proper  acid 
and  ferment.  \ 

The  secretion,  as  we  have  seen,  completely  dissolves 
albumen,  muscle,  fibrin,  areolar  tissue,  cartilage,  the 
fibrous  basis  of  bone,  gelatin,  chondrin,  casein  in  the 
state  in  which  it  exists  in  milk,  and  gluten  which  has 
been  subjected  to  weak  hydrochloric  acid.  Syntonin 
and  legumin  excite  the  leaves  so  powerfully  and 
(piickly  that  there  can  hardly  be  a doubt  that  both 
would  be  dissolved  by  the  secretion.  The  secretion 


♦ ^ Phys.  de  la  Digestion/  1867,  tom.  ii.  pp.  188,  245. 


130 


DROSERA  ROTUNDIFOLIA. 


Chap.  VI. 


failed  to  digest  fresh  gluten,  apparently  from  its 
injuring  the  glands,  though  some  was  absorbed.  Kaw 
meat,  unless  in  very  small  bits,  and  large  pieces  of 
albumen,  &c.,  likewise  injure  the  leaves,  which  seem 
to  suffer,  like  animals,  from  a surfeit.  I know  not 
whether  the  analogy  is  a real  one,  but  it  is  worth 
notice  that  a decoction  of  cabbage  leaves  is  far  more 
exciting  and  probably  nutritious  to  Drosera  than  an 
infusion  made  with  tepid  water ; and  boiled  cabbages 
are  far  more  nutritious,  at  least  to  man,  than  the  un- 
cooked leaves.  The  most  striking  of  all  the  cases, 
though  not  really  more  remarkable  than  many  others, 
is  the  digestion  of  so  hard  and  tough  a substance  as 
cartilage.  The  dissolution  of  pure  phosphate  of  lime, 
of  bone,  dentine,  and  especially  enamel,  seems  won- 
derful ; but  it  depends  merely  on  the  long-continued 
secretion  of  an  acid ; and  this  is  secreted  for  a longer 
time  under  these  circumstances  than  under  any  others, 
^t  was  interesting  to  observe  that  as  long  as  the  acid 
was  consumed  in  dissolving  the  phosphate  of  lime,  no 
true  digestion  occurred ; but  that  as  soon  as  the  bone 
was  completely  decalcified,  the  fibrous  basis  was  at- 
tacked and  liquefied  with  the  greatest  ease.^  The 
twelve  substances  above  enumerated,  which  are  com- 
pletely dissolved  by  the  secretion,  are  likewise  dis- 
solved by  the  gastric  juice  of  the  higher  animals ; 
and  they  are  acted  on  in  the  same  manner,  as  shown 
by  the  rounding  of  the  angles  of  albumen,  and  more 
especially  by  the  manner  in  w^hich  the  transverse  stri/e 
of  the  fibres  of  muscle  disappear. 

The  secretion  of  Drosera  and  gastric  juice  were 
both  able  to  dissolve  some  element  or  impurity  out  of 
the  globulin  and  hsematin  employed  by  me.  The 
secretion  also  dissolved  something  out  of  chemically 


Chap.  VI. 


DIGESTION. 


131 


prepared  casein,  which,  is  said  to  consist  of  two  sub- 
stances ; and  although  Schiff  asserts  that  casein  in 
this  state  is  not  attacked  by  gastric  juice,  he  might 
easily  have  overlooked  a minute  quantity  of  some 
albuminous  matter,  which  Drosera  would  detect  and 
absorb.  Again,  fibro-cartilage,  though  not  properly 
dissolved,  is  acted  on  in  the  same  manner,  both  by 
the  secretion  of  Drosera  and  gastric  juice.  But  this 
substance,  as  well  as  the  so-called  haematin  used  by 
me,  ought  perhaps  to  have  been  classed  with  indi- 
gestible substances. 

sThat  gastric  juice  acts  by  means  of  its  ferment, 
pepsin,  solely  in  the  presence  of  an  acid,  is  well 
established;  and  we  have  excellent  evidence  that  a 
ferment  is  present  in  the  secretion  of  Drosera,  which 
likewise  acts  only  in  the  presence  of  an  acid ; for  we 
have  seen  that  when  the  secretion  is  neutralised  by 
minute  drops  of  the  solution  of  an  alkali,  the  diges- 
tion of  albumen  is  completely  stopped,  and  that  on 
the  addition  of  a minute  dose  of  hydrochloric  acid  it 
immediately  recommences.  ^ 

The  nine  following  substances,  or  classes  of  sub- 
stances, namely,  epidermic  productions,  fibro-elastic 
tissue,  mucin,  pepsin,  urea,  chitine,  cellulose,  gun 
cotton,  chlorophyll,  starch,  fat  and  oil,  are  not  acted 
on  by  the  secretion  of  Drosera ; nor  are  they,  as  far  as 
is  known,  by  the  gastric  juice  of  animals.  Some 
soluble  matter,  however,  was  extracted  from  the  mucin, 
pepsin,  and  chlorophyll,  used  by  me,  both  by  the 
secretion  and  by  artificial  gastric  juice. 

The  several  substances,  which  are  completely  dis- 
solved by  the  secretion,  and  which  are  afterwards 
absorbed  by  the  glands,  affect  the  leaves  rather  dif- 
ferently. They  induce  inflection  at  very  different 


132 


DROSERA  ROTUNDIFOLIA. 


Chap.  VL 


rates  and  in  very  different  degrees ; and  the  ten- 
tacles remain  inflected  for  very  different  periods  of 
time.  Quick  inflection  depends  partly  on  the  quan- 
' tity  of  the  substance  given,  so  that  many  glands  are 
simultaneously  affected,  partly  on  the  facility  with 
which  it  is  penetrated  and  liquefied  by  the  secretion, 
partly  on  its  nature,  but  chiefly  on  the  presence  of 
exciting  matter  already  in  solution.  Thus  saliva,  or 
a weak  solution  of  raw  meat,  acts  much  more  quickly 
than  even  a strong  solution  of  gelatine.  So  again 
leaves  which  have  re-expanded,  after  absorbing  drops 
of  a solution  of  pure  gelatine  or  isinglass  (the  latter 
being  the  more  powerful  of  the  two),  if  given  bits 
of  meat,  are  inflected  much  more  energetically  and 
quickly  than  they  were  before,  notwithstanding  that 
some  rest  is  generally  requisite  between  two  acts 
of  inflection.  We  probably  see  the  influence  of  tex- 
ture in  gelatine  and  globulin  when  softened  by 
having  been  soaked  in  water  acting  more  quickly 
than  when  merely  wetted.  It  may  be  partly  due  to 
changed  texture,  and  partly  to  changed  chemical 
nature,  that  albumen,  which  has  been  kept  for  some 
time,  and  gluten  which  has  been  subjected  to  weak 
hydrochloric  acid,  act  more  quickly  than  these  sub- 
ystances  in  their  fresh  state. 

The  length  of  time  during  which  the  tentacles  re- 
main inflected  largely  depends  on  the  quantity  of  the 
substance  given,  partly  on  the  facility  with  which  it  is 
penetrated  or  acted  on  by  the  secretion,  and  partly 
on  its  essential  nature.  The  tentacles  always  remain 
inflected  much  longer  over  large  bits  or  large  drops 
than  over  small  bits  or  drops.  Texture  probably 
plays  a part  in  determining  the  extraordinary  length 
of  time  during  which  the  tentacles  remain  inflected 


Chap.  VI. 


DIGESTION. 


133 


over  the  hard  grains  of  chemically  prepared  casein. 
But  the  tentacles  remain  inflected  for  an  equally  long 
time  over  finely  powdered,  precipitated  phosphate  of 
lime ; phosphorus  in  this  latter  case  evidently  being 
the  attraction,  and  animal  matter  in  the  case  of  casein. 
The  leaves  remain  long  inflected  over  insects,  but  it  is 
doubtful  how  far  this  is  due  to  the  protection  afforded 
by  their  chitinous  integuments ; for  animal  matter  is 
soon  extracted  from  insects  (probably  by  exosmose  from 
their  bodies  into  the  dense  surrounding  secretion), 
as  shown  by  the  prompt  inflection  of  the  leaves.  We 
see  the  influence  of  the  nature  of  different  substances 
in  bits  of  meat,  albumen,  and  fresh  gluten  acting  very 
differently  from  equal-sized  bits  of  gelatine,  areolar 
tissue,  and  the  fibrous  basis  of  bone.  The  former 
cause  not  only  far  more  prompt  and  energetic,  but 
more  prolonged,  inflection  than  do  the  latter.  Hence 
we  are,  I think,  justified  in  believing  that  gelatine, 
areolar  tissue,  and  the  fibrous  basis  of  bone,  would  be 
far  less  nutritious  to  Drosera  than  such  substances 
as  insects,  meat,  albumen,  &c.  This  is  an  interest- 
ing conclusion,  as  it  is  known  that  gelatine  affords 
but  little  nutriment  to  animals ; and  so,  probably, 
would  areolar  tissue  and  the  fibrous  basis  of  bone. 
The  chondrin  which  I used  acted  more  powerfully 
than  gelatine,  but  then  I do  not  know  that  it  was 
pure.  It  is  a more  remarkable  fact  that  fibrin,  which 
belongs  to  the  great  class  of  Proteids,*  including 
albumen  in  one  of  its  sub-groups,  does  not  excite 
the  tentacles  in  a greater  degree,  or  keep  them  in- 
flected for  a longer  time,  than  does  gelatine,  or 


* See  the  classification  adopted  by  Dr.  Michael  Foster  in  Watts’ 
Diet,  of  Chemistry/  Supplement  1872,  p.  969. 


134 


DROSEKA  ROTUNDIFOLIA. 


Chap.  VI. 


areolar  tissue,  or  the  fibrous  basis  of  bone.  It  is  not 
known  how  long  an  animal  would  survive  if  fed  on 
fibrin  alone,  but  Dr.  Sanderson  has  no  doubt  longer 
than  on  gelatine,  and  it  would  be  hardly  rash  to  pre- 
dict, judging  from  the  effects  on  Drosera,  that  albu- 
men would  be  found  more  nutritious  than  fibrin. 
Globulin  likewise  belongs  to  the  Proteids,  forming 
another  sub-group,  and  this  substance,  though  con- 
taining some  matter  which  excited  Drosera  rather 
strongly,  was  hardly  attacked  by  the  secretion,  and 
was  very  little  or  very  slowly  attacked  by  gastric 
juice.  How  far  globulin  would  be  nutritious  to  ani- 
mals is  not  known.  We  thus  see  how  differently  the 
above  specified  several  digestible  substances  act  on 
Drosera ; and  we  may  infer,  as  highly  probable,  that 
they  would  in  like  manner  be  nutritious  in  very  dif- 
ferent degrees  both  to  Drosera  and  to  animals. 

The  glands  of  Drosera  absorb  matter  from  living 
seeds,  which  are  injured  or  killed  by  the  secretion. 
They  likewise  absorb  matter  from  pollen,  and  from 
fresh  leaves ; and  this  is  notoriously  the  case  with 
the  stomachs  of  vegetable-feeding  animals.  Drosera 
is  properly  an  insectivorous  plant;  but  as  pollen 
cannot  fail  to  be  often  blown  on  to  the  glands,  as 
will  occasionally  the  seeds  and  leaves  of  surrounding 
plants,  Drosera  is,  to  a certain  extent,  a vegetable- 
feeder. 

/ Finally,  the  experiments  recorded  in  this  chapter 
show  us  that  there  is  a remarkable  accordance  in  the 
power  of  digestion  between  the  gastric  juice  of  ani- 
mals with  its  pepsin  and  hydrochloric  acid  and  the 
secretion  of  Drosera  with  its  ferment  and  acid  belong- 
ing to  the  acetic  series.  We  can,  therefore,  hardly 
doubt  that  the  ferment  in  both  cases  is  closely  similar, 


Chap.  VI. 


DIGESTION. 


135 


if  not  identically  the  same.  That  a plant  and  an 
animal  should  pour  forth  the  same,  or  nearly  the  same, 
complex  secretion,  adapted  for  the  same  purpose  of 
digestion,  is  a new  and  wonderful  fact  in  physiology. 
But  I shall  have  to  recur  to  this  subject  in  the 
fifteenth  chapter,  in  my  concluding  remarks  on  the 
Droseraceae. 


7 


136 


DROSEBA  EOTUNDIFOLIA. 


Chap.  VIL 


CHAPTEE  VII. 

The  Effects  of  Salts  of  Ammonia. 

Manner  of  performing  the  experiments  — Action  of  distilled  water  in 
comparison  with  the  solutions  — Carbonate  of  ammonia,  absorbed 
by  the  roots  — The  vapour  absorbed  by  the  glands  — Drops  on  the 
disc  — Minute  drops  applied  to  separate  glands  — Leaves  im- 
mersed in  weak  solutions  — Minuteness  of  the  doses  which  induce 
aggregation  of  the  protoplasm  — Nitrate  of  ammonia,  analogous 
experiments  with  — Phosphate  of  ammonia,  analogous  experiments 
with  — Other  salts  of  ammonia  — Summary  and  concluding  re- 
marks on  the  action  of  the  salts  of  ammonia. 

The  chief  object  in  this  chapter  is  to  show  how  power- 
fully the  salts  of  ammonia  act  on  the  leaves  of  Drosera, 
and  more  especially  to  show  what  an  extraordinarily 
small  quantity  suffices  to  excite  inflection.  I shall, 
therefore,  be  compelled  to  enter  into  full  details. 
Doubly  distilled  water  was  always  used ; and  for  the 
more  delicate  experiments,  water  which  had  been 
prepared  with  the  utmost  possible  care  was  given 
me  by  Professor  Frankland.  The  graduated  measures 
were  tested,  and  found  as  accurate  as  such  measures 
can  be.  The  salts  were  carefully  weighed,  and  in  all 
the  more  delicate  experiments,  by  Bor  da’s  double 
method.  But  extreme  accuracy  would  have  been 
superfluous,  as  the  leaves  differ  greatly  in  irritability, 
according  to  age,  condition,  and  constitution.  Even 
the  tentacles  on  the  same  leaf  differ  in  irritability 
to  a marked  degree.  My  experiments  were  tried  in 
the  following  several  ways. 

Fnstly. —Dro^s  which  were  ascertained  by  repeated  trials  to 
be  on  an  average  about  half  a minim,  or  the  of  a fluid  ounce 
( 0296  ml.),  were  placed  by  the  same  pointed  instrument  on  the 


Chap.  VII. 


SALTS  OF  AMMONIA. 


137 


discs  of  the  leaves,  and  the  inflection  of  the  exterior  rows  of 
tentacles  observed  at  successive  intervals  of  time.  It  was  first 
ascertained,  from  between  thirty  and  forty  trials,  that  distilled 
water  dropped  in  this  manner  produces  no  effect,  except  that 
sometimes,  though  rarely,  two  or  three  tentacles  become  in- 
flected. In  fact  all  the  many  trials  with  solutions  which  were 
so  weak  as  to  produce  no  effect  lead  to  the  same  result  that 
water  is  inefficient. 

Secondly,— head  of  a small  pin,  fixed  into  a handle,  was 
dipped  into  the  solution  under  trial.  The  small  drop  which 
adhered  to  it,  and  which  was  much  too  small  to  fall  off,  was 
cautiously  placed,  by  the  aid  of  a lens,  in  contact  with  the  secre- 
tion surrounding  the  glands  of  one,  two,  three,  or  four  of  the 
exterior  tentacles  of  the  same  leaf.  Great  care  was  taken  that 
the  glands  themselves  should  not  be  touched.  I had  supposed 
that  the  drops  were  of  nearly  the  same  size ; but  on  trial  this 
proved  a great  mistake.  I first  measured  some  water,  and  re- 
moved 300  drops,  touching  the  pin’s  head  each  time  on  blotting- 
paper  ; and  on  again  measuring  the  water,  a drop  was  found  to 
equal  on  an  average  about  the  of  a minim.  Some  water  in  a 
small  vessel  was  weighed  (and  this  is  a more  accurate  method), 
and  300  drops  removed  as  before ; and  on  again  weighing  the 
water,  a drop  was  found  to  equal  on  an  average  only  the 
of  a minim.  I repeated  the  operation,  but  endeavoured  this 
time,  by  taking  the  pin’s  head  out  of  the  water  obliquely  and 
rather  quickly,  to  remove  as  large  drops  as  possible ; and 
the  result  showed  that  I had  succeeded,  for  each  drop  on  an 
average  equalled  7^  of  a minim.  I repeated  the  operation  in 
exactly  the  same  manner,  and  now  the  drops  averaged  77.7  of  a 
minim.  Bearing  in  mind  that  on  these  two  latter  occasions 
special  pains  were  taken  to  remove  as  large  drops  as  possible, 
we  may  safely  conclude  that  the  drops  used  in  my  experiments 
were  at  least  equal  to  the  of  a minim,  or  *0029  ml.  One  of 
these  drops  could  be  applied  to  three  or  even  four  glands,  and 
if  the  tentacles  became  inflected,  some  of  the  solution  must 
have  been  absorbed  by  all;  for  drops  of  pure  water,  applied 
in  the  same  manner,  never  produced  any  effect.  I was  able  to 
hold  the  drop  in  steady  contact  with  the  secretion  only  for  ten 
to  fifteen  seconds ; and  this  was  not  time  enough  for  the  diffu- 
sion of  all  the  salt  in  solution,  as  was  evident,  from  three  or 
four  tentacles  treated  successively  with  the  same  drop,  often 
becoming  inflected.  All  the  matter  in  solution  was  even  then 
probably  not  exhausted. 

Thirdly. — Leaves  were  cut  off  and  immersed  in  a measured 


138 


DEOSERA  ROTUNDIFOLIA. 


CuAP.  XIL 


quantity  of  the  solution  under  trial ; the  same  number  of  leaves 
being  immersed  at  the  same  time,  in  the  same  quantity  of  the 
distilled  water  which  had  been  used  in  making  the  solution. 
The  leaves  in  the  two  lots  were  compared  at  short  intervals 
of  time,  up  to  24  hrs.,  and  sometimes  to  48  hrs.  They  were 
immersed  by  being  laid  as  gently  as  possible  in  numbered 
watch-glasses,  and  thirty  minims  (1*775  ml.)  of  the  solution 
or  of  water  was  poured  over  each. 

Some  solutions,  for  instance  that  of  carbonate  of  ammonia, 
quickly  discolour  the  glands ; and  as  all  on  the  same  leaf  were 
discoloured  simultaneously,  they  must  all  have  absorbed  some 
of  the  salt  within  the  same  short  period  of  time.  This  was 
likewise  shown  by  the  simultaneous  inflection  of  the  several 
exterior  rows  of  tentacles.  If  we  had  no  such  evidence  as 
this,  it  might  have  been  supposed  that  only  the  glands  of  the 
exterior  and  inflected  tentacles  had  absorbed  the  salt;  or  that 
only  those  on  the  disc  had  absorbed  it,  and  had  then  transmitted 
a motor  impulse  to  the  exterior  tentacles ; but  in  this  latter  case 
the  exterior  tentacles  would  not  have  become  inflected  until 
some  time  had  elapsed,  instead  of  within  half  an  hour,  or  even 
within  a few  minutes,  as  usually  occurred.  All  the  glands  on 
the  same  leaf  are  of  nearly  the  same  size,  as  may  best  be  seen 
by  cutting  off  a narrow  transverse  strip,  and  laying  it  on  its 
side;  hence  their  absorbing  surfaces  are  nearly  equal.  The 
long-headed  glands  on  the  extreme  margin  must  be  excepted, 
as  they  are  much  longer  than  the  others;  but  only  the  upper 
surface  is  capable  of  absorption.  Besides  the  glands,  both 
surfaces  of  the  leaves  and  the  pedicels  of  the  tentacles  bear 
numerous  minute  papillae,  which  absorb  carbonate  of  ammonia, 
an  infusion  of  raw  meat,  metallic  salts,  and  probably  many 
other  substances,  but  the  absorption  of  matter  by  these  papillae 
never  induces  inflection.  We  must  remember  that  the  move- 
ment of  each  separate  tentacle  depends  on  its  gland  being 
excited,  except  when  a motor  impulse  is  transmitted  from  the 
glands  of  the  disc,  and  then  the  movement,  as  just  stated, 
does  not  take  place  until  some  little  time  has  elapsed.  I have 
made  these  remarks  because  they  show  us  that  when  a leaf  is 
immersed  in  a solution,  and  the  tentacles  are  inflected,  we  can 
judge  with  some  accuracy  how  much  of  the  salt  each  gland  has 
absorbed.  For  instance,  if  a leaf  bearing  212  glands  be  immersed 
in  a measured  quantity  of  a solution,  containing  ^ of  a grain  of 
a salt,  and  all  the  exterior  tentacles,  except  twelve,  are  inflected, 
we  may  feel  sure  that  each  of  the  200  glands  can  on  an  average 
have  absorbed  at  most  of  a grain  of  the  salt.  I say  at 


Chap.  VIL 


EFFECTS  OF  WATER. 


139 


most,  for  the  papillae  will  have  absorbed  some  small  amount, 
and  so  will  perhaps  the  glands  of  the  twelve  excluded  tentacles 
which  did  not  become  inflected.  The  application  of  this  prin- 
ciple leads  to  remarkable  conclusions  with  respect  to  the 
minuteness  of  the  doses  causing  inflection. 

On  the  Action  of  Distilled  Water  in  causing  hifiection. 

Although  in  all  the  more  important  experiments  the  dif- 
ference between  the  leaves  simultaneously  immersed  in  water 
and  in  the  several  solutions  will  be  described,  nevertheless  it 
may  be  well  here  to  give  a summary  of  the  effects  of  water. 
The  fact,  moreover,  of  pure  water  acting  on  the  glands  deserves 
in  itself  some  notice.  Leaves  to  the  number  of  141  were  im- 
mersed in  water  at  the  same  time  with  those  in  the  solutions, 
and  their  state  recorded  at  short  intervals  of  time.  Thirty-two 
other  leaves  were  separately  observed  in  water,  making  alto- 
gether 173  experiments.  Many  scores  of  leaves  were  also  im- 
mersed in  water  at  other  times,  but  no  exact  record  of  the 
effects  produced  was  kept ; yet  these  cursory  observations  sup- 
port the  conclusions  arrived  at  in  this  chapter.  A few  of  the 
long-headed  tentacles,  namely  from  one  to  about  six,  were 
commonly  inflected  within  half  an  hour  after  immersion;  as 
were  occasionally  a few,  and  rarely  a considerable  number  of 
the  exterior  round-headed  tentacles.  After  an  immersion  of 
from  5 to  8 hrs.  the  short  tentacles  surrounding  the  outer 
parts  of  the  disc  generally  become  inflected,  so  that  their  glands 
form  a small  dark  ring  on  the  disc;  the  exterior  tentacles 
not  partaking  of  this  movement.  Hence,  excepting  in  a few 
cases  hereafter  to  be  specified,  we  can  judge  whether  a solution 
produces  any  effect  only  by  observing  the  exterior  tentacles 
within  the  first  3 or  4 hrs.  after  immersion. 

Now  for  a summary  of  the  state  of  the  173  leaves  after  an 
immersion  of  3 or  4 hrs.  in  pure  water.  One  leaf  had  almost 
all  its  tentacles  inflected ; three  leaves  had  most  of  them  sub- 
inflected; and  thirteen  had  on  an  average  36*5  tentacles  in- 
flected. Thus  seventeen  leaves  out  of  the  173  were  acted  on  in 
a marked  manner.  Eighteen  leaves  had  from  seven  to  nineteen 
tentacles  inflected,  the  average  being  9*3  tentacles  for  each 
leaf.  Forty-four  leaves  had  from  one  to  six  tentacles  inflected, 
generally  the  long-headed  ones.  So  that  altogether  of  the  173 
leaves  carefully  observed,  seventy-nine  were  affected  by  the 
water  in  some  degree  though  commonly  to  a very  slight  degree ; 
and  ninety-four  were  not  affected  in  the  least  degree.  Thij? 


140 


DROSEKA  ROTUNDIFOLIA. 


Chap.  VII. 


amount  of  inflection  is  utterly  insignificant,  as  we  shall  here- 
after see,  compared  with  that  caused  by  very  weak  solutions 
of  several  salts  of  ammonia. 

Plants  which  have  lived  for  some  time  in  a rather  high 
temperature  are  far  more  sensitive  to  the  action  of  water  than 
those  grown  out  of  doors,  or  recently  brought  into  a warm 
greenhouse.  Thus  in  the  above  seventeen  cases,  in  which  the 
immersed  leaves  had  a considerable  number  of  tentacles  in- 
flected, the  plants  had  been  kept  during  the  winter  in  a very 
warm  greenhouse ; and  they  bore  in  the  early  spring  remarkably 
fine  leaves,  of  a light  red  colour.  Had  I then  known  that  the 
sensitiveness  of  plants  was  thus  increased,  perhaps  I should 
not  have  used  the  leaves  for  my  experiments  with  the  very 
weak  solutions  of  phosphate  of  ammonia ; but  my  experiments 
are  not  thus  vitiated,  as  I invariably  used  leaves  from  the  same 
plants  for  simultaneous  immersion  in  water.  It  often  happened 
that  some  leaves  on  the  same  plant,  and  some  tentacles  on  the 
same  leaf,  were  more  sensitive  than  others ; but  why  this  should 
be  so,  I do  not  know. 

Besides  the  differences  just  indicated  between  the  leaves  im- 
mersed in  water  and  in  weak 
solutions  of  ammonia,  the  ten- 
tacles of  the  latter  are  in  most 
cases  much  more  closely  in- 
flected. The  appearance  of  a 
leaf  after  immersion  in  a few 
drops  of  a solution  of  one  grain 
of  phosphate  of  ammonia  to 
200  oz.  of  water  (i,e.  one  part 
to  87,500)  is  here  reproduced  : 
such  energetic  inflection  is 
never  caused  by  water  alone. 
With  leaves  in  the  weak  solu- 
tions, the  blade  or  lamina  often 
becomes  inflected ; and  this  is 
so  rare  a circumstance  with 
leaves  in  water  that  I have 
seen  only  two  instances;  and 
in  both  of  these  the  inflec- 
tion was  very  feeble.  Again 
with  leaves  in  the  weak  solu 
tions,  the  inflection  of  the  ten- 
tacles and  blade  often  goes  on 
steadily,  though  slo^yly,  increasing  during  many  hours;  and 


Fig.  9. 

{^Drosera  rotundifolia.) 

^eaf  (enlarged)  with  all  the  tentacles 
closely  inflected,  from  immersion  in  a 
solution  of  phosphate  of  ammonia  (one 
part  to  87,500  of  water)» 


Chap.  VIL 


CARBONATE  OF  AMMONIA. 


141 


this  again  is  so  rare  a circumstance  with  leaves  in  water  that 
I have  seen  only  three  instances  of  any  such  increase  after  the 
first  8 to  12  hrs. ; and  in  these  three  instances  the  two  outer 
rows  of-  tentacles  were  not  at  all  affected.  Hence  there  is  some- 
times a much  greater  difference  between  the  leaves  in  water  and 
in  the  weak  solutions,  after  from  8 hrs.  to  24  hrs.,  than  there 
was  within  the  first  3 hrs. ; though  as  a general  rule  it  is  best 
to  trust  to  the  difference  observed  within  the  shorter  time. 

With  respect  to  the  period  of  the  re-expansion  of  the  leaves, 
when  left  immersed  either  in  water  or  in  the  weak  solutions, 
nothiDg  could  be  more  variable.  In  both  cases  the  exterior 
tentacles  not  rarely  begin  to  re-expand,  after  an  interval  of 
only  from  6 to  8 hrs. ; that  is  just  about  th^e  time  when  the 
short  tentacles  round  the  borders  of  the  disc  become  inflected. 
On  the  other  hand,  the  tentacles  sometimes  remain  inflected 
for  a whole  day,  or  even  two  days ; but  as  a general  rule  they 
remain  inflected  for  a longer  period  in  very  weak  solutions  than 
in  water.  In  solutions  which  are  not  extremely  weak,  they 
never  re-expand  within  nearly  so  short  a period  as  six  or 
eight  hours.  From  these  statements  it  might  be  thought 
difficult  to  distinguish  between  the  effects  of  water  and  the 
weaker  solutions ; but  in  truth  there  is  not  the  slightest  diffi- 
culty until  excessively  weak  solutions  are  tried ; and  then  the 
distinction,  as  might  be  expected,  becomes  very  doubtful,  and 
at  last  disappears.  But  as  in  all,  except  the  simplest,  cases 
the  state  of  the  leaves  simultaneously  immersed  for  an  equal 
length  of  time  in  water  and  in  the  solutions  will  be  described, 
the  reader  can  judge  for  himself. 

Carbonate  of  Ammonia. 

This  salt,  when  absorbed  by  the  roots,  does  not  cause 
the  tentacles  to  be  inflected.  A plant  was  so  placed 
in  a solution  of  one  part  of  the  carbonate  to  146  of 
water  that  the  young  uninjured  roots  could  be  ob- 
served. The  terminal  cells,  which  were  of  a pink 
colour,  instantly  became  colourless,  and  their  limpid 
contents  cloudy,  like  a mezzo-tinto  engraving,  so  that 
some  degree  of  aggregation  was  almost  instantly 
caused;  but  no  further  change  ensued,  and  the  ab- 
sorbent hairs  were  not  visibly  affected.  The  tentacles 


142 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


did  not  bend.  Two  other  plants  were  placed  with 
their  roots  surrounded  by  damp  moss,  in  half  an  ounce 
(14’198  ml.)  of  a solution  of  one  part  of  the  carbo- 
nate to  218  of  water,  and  were  observed  for  24  hrs. ; 
but  not  a single  tentacle  was  inflected.  In  order  to 
produce  this  efl’ect,  the  carbonate  must  be  absorbed 
by  the  glands. 

'^The  vapour  produces  a powerful  effect  on  the  glands, 
and  induces  inflection.  Three  plants  with  their  roots 
in  bottles,  so  that  the  surrounding  air  could  not  have 
become  very  humid,  were  placed  under  a bell-glass 
(holding  122  fluid  ounces),  together  with  4 grains 
of  carbonate  of  ammonia  in  a watch-glass.  After  an 
interval  of  6 hrs.  15  m.  the  leaves  appeared  unaffected ; 
but  next  morning,  after  20  hrs.,  the  blackened  glands 
were  secreting  copiously,  and  most  of  the  tentacles 
were  strongly  inflected.  These  plants  soon  died. 
Two  other  plants  were  placed  under  the  same  bell- 
glass,  together  with  half  a grain  of  the  carbonate,  the 
air  being  rendered  as  damp  as  possible  ; and  in  2 hrs. 
most  of  the  leaves  were  affected,  many  of  the  glands 
being  blackened  and  the  tentacles  inflected.  But  it  is 
a curious  fact  that  some  of  the  closely  adjoining  ten- 
tacles on  the  same  leaf,  both  on  the  disc  and  round 
the  margins,  were  much,  and  some,  apparently,  not  in 
the  least  affected.  The  plants  were  kept  under  the 
bell-glass  for  24  hrs.,  but  no  further  change  ensued. 
One  healthy  leaf  was  hardly  at  all  affected,  though 
other  leaves  on  the  same  plant  were  much  affected. 
On  some  leaves  all  the  tentacles  on  one  side,  but  not 
those  on  the  opposite  side,  were  inflected.  I doubt 
whether  this  extremely  unequal  action  can  be  ex- 
plained by  supposing  that  the  more  active  glands 
absorb  all  the  vapour  as  quickly  as  it  is  generated,  so 
that  none  is  left  for  the  others  for  we  shall  meet  with 


Chap.  VII. 


CARBONATE  OF  AMMONIA. 


143 


analogous  cases  with  air  thoroughly  permeated  with 
the  vapours  of  chloroform  and  ether. 

Minute  particles  of  the  carbonate  were  added  to  the 
secretion  surrounding  several  glands.  These  instantly 
became  black  and  secreted  copiously ; but,  except  in 
two  instances,  when  extremely  minute  particles  were 
given,  there  was  no  inflection.  This  result  is  analo- 
gous to  that  which  follows  from  the  immersion  of 
leaves  in  a strong  solution  of  one  part  of  the  carbonate 
to  109,  or  146,  or  even  218  of  water,  for  the  leaves 
are  then  paralysed  and  no  inflection  ensues,  though 
the  glands  are  blackened,  and  the  protoplasm  in  the 
cells  of  the  tentacles  undergoes  strong  aggregation. 


We  will  now  turn  to  the  effects  of  solutions  of  the  carbonate. 
Half-minims  of  a solution  of  one  part  to  437  of  water  were  placed 
on  the  discs  of  twelve  leaves ; so  that  each  received  of  a grain 
or  *0675  mg.  Ten  of  these  had  their  exterior  tentacles  well 
inflected ; the  blades  of  some  being  also  much  curved  inwards. 
In  two  cases  several  of  the  exterior  tentacles  were  inflected  in 
35  m. ; but  the  movement  was  generally  slower.  These  ten 
leaves  re-expanded  in  periods  varying  between  21  hrs.  and 
45  hrs.,  but  in  one  case  not  until  67  hrs.  had  elapsed ; so  that 
they  re-expanded  much  more  quickly  than  leaves  which  have 
caught  insects. 

The  same-sized  drops  of  a solution  of  one  part  to  875  of  water 
were  placed  on  the  discs  of  eleven  leaves;  six  remained  quite 
unaffected,  whilst  five  had  from  three  to  six  or  eight  of  their 
exterior  tentacles  inflected;  but  this  degree  of  movement  can 
hardly  be  considered  as  trustworthy.  Each  of  these  leaves 
received  rm  of  ^ grain  (*0337  mg.),  distributed  between  the 
glands  of  the  disc,  but  this  was  too  small  an  amount  to  produce 
any  decided  effect  on  the  exterior  tentacles,  the  glands  of  which 
had  not  themselves  received  any  of  the  salt. 

Minute  drops  on  the  head  of  a small  pin,  of  a solution  of  one 
part  of  the  carbonate  to  218  of  water,  were  next  tried  in  the 
manner  above  described.  A drop  of  this  kind  equals  on  an 
average  of  a minim,  and  therefore  contains  of  a grain 
(*0135  mg.)  of  the  carbonate.  I touched  with  it  the  viscid 
secretion  round  three  glands,  so  that  each  gland  received  onlj 


144 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIL 


14 of  a grain  (*00445  mg.).  Nevertheless,  in  two  trials  all 
the  glands  were  plainly  blackened ; in  one  case  all  three  tentacles 
were  well  inflected  after  an  interval  of  2 hrs.  40  m. ; and  in  an- 
other case  two  of  the  three  tentacles  were  inflected.  I then 
tried  drops  of  a weaker  solution  of  one  part  to  292  of  water  on 
twenty-four  glands,  always  touching  the  viscid  secretion  round 
three  glands  with  the  same  little  drop.  Each  gland  thus  received 
only  the  T9I00  ^ grain  (*00337  mg.),  yet  some  of  them  were 

a little  darkened ; but  in  no  one  instance  were  any  of  the  ten- 
tacles inflected,  though  they  were  watched  for  12  hrs.  When  a 
still  weaker  solution  (viz.  one  part  to  437  of  water)  was  tried  on 
six  glands,  no  effect  whatever  was  perceptible.  We  thus  learn 
that  the  14^^  of  a grain  (*00445  mg.)  of  carbonate  of  ammonia, 
if  absorbed  by  a gland,  suffices  to  induce  inflection  in  the  basal 
part  of  the  same  tentacle ; but  as  already  stated,  I was  able  to 
hold  with  a steady  hand  the  minute  drops  in  contact  with  the 
secretion  only  for  a few  seconds;  and  if  more  time  had  been 
allowed  for  diffusion  and  absorption,  a much  weaker  solution 
would  certainly  have  acted. 

Some  experiments  were  made  by  immersing  cut-off  leaves  in 
solutions  of  different  strengths.  Thus  four  leaves  were  left  for 
about  3 hrs.  each  in  a drachm  (3  * 549  ml.)  of  a solution  of  one 
part  of  the  carbonate  to  5250  of  water ; two  of  these  had  almost 
every  tentacle  inflected,  the  third  had  about  half  the  tentacles 
and  the  fourth  about  one- third  inflected ; and  all  the  glands  were 
blackened.  Another  leaf  was  placed  in  the  same  quantity  of  a 
solution  of  one  part  to  7000  of  water,  and  in  1 hr.  16  m.  every 
single  tentacle  was  well  inflected,  and  all  the  glands  blackened. 
Six  leaves  were  immersed,  each  in  thirty  minims  (1*774  ml.)  of 
a solution  of  one  part  to  4375  of  water,  and  the  glands  were  all 
blackened  in  31  m.  All  six  leaves  exhibited  some  slight  inflec- 
tion, and  one  was  strongly  inflected.  Four  leaves  were  then 
immersed  in  thirty  minims  of  a solution  of  one  part  to  8750  of 
water,  so  that  each  leaf  received  the  of  a grain  (*2025  mg.). 
Only  one  became  strongly  inflected ; but  all  the  glands  on  all 
the  leaves  were  of  so  dark  a red  after  one  hour  as  almost  to 
deserve  to  be  called  black,  whereas  this  did  not  occur  with  the 
leaves  which  were  at  the  same  time  immersed  in  water ; nor  did 
water  produce  this  effect  on  any  other  occasion  in  nearly  so 
short  a time  as  an  hour.  These  cases  of  the  simultaneous 
darkening  or  blackening  of  the  glands  from  the  action  of  weak 
solutions  are  important,  as  they  show  that  all  the  glands  absorbed 
the  carbonate  within  the  same  time,  which  fact  indeed  there 
was  not  the  least  reason  to  doubt.  So  again,  whenever  all  the 


Chap.  VII. 


CAKBONATE  OP  AMMONIA. 


145 


tentacles  become  inflected  within  the  same  time,  we  have 
evidence,  as  before  remarked,  of  simnltaneons  absorption.  I 
did  not  count  the  number  of  glands  on  these  four  leaves ; but 
as  they  were  fine  ones,  and  as  we  know  that  the  average  number 
of  glands  on  thirty-one  leaves  was  192,  we  may  safely  assume 
that  each  bore  on  an  average  at  least  170;  and  if  so,  each 
blackened  gland  could  have  absorbed  only  of  a grain 

( * 00119  mg.)  of  the  carbonate. 

A large  number  of  trials  had  been  previously  made  with 
solutions  of  one  part  of  the  nitrate  and  phosphate  of  ammonia  to 
43750  of  water  (i.e.  one  grain  to  100  ounces),  and  these  were 
found  highly  efficient.  Fourteen  leaves  were  therefore  placed, 
each  in  thirty  minims  of  a solution  of  one  part  of  the  carbonate 
to  the  above  quantity  of  water ; so  that  each  leaf  received 
of  a grain  (*0405  mg.).  The  glands  were  not  much  darkened. 
Ten  of  the  leaves  were  not  affected,  or  only  very  slightly  so. 
Four,  however,  were  strongly  affected ; the  first  having  all  the 
tentacles,  except  forty,  inflected  in  47  m. ; in  6 hrs.  30  m.  all 
except  eight ; and  after  4 hrs.  the  blade  itself.  The  second  leaf 
after  9 m.  had  all  its  tentacles  except  nine  inflected ; after  6 hrs. 
30  m.  these  nine  were  sub-inflected ; the  blade  having  become 
much  inflected  in  4 hrs.  The  third  leaf  after  1 hr.  6 m.  had  all 
but  forty  tentacles  inflected.  The  fourth,  after  2 hrs.  5 m.,  had 
about  half  its  tentacles  and  after  4 hrs.  all  but  forty-five  in- 
flected. Leaves  which  were  immersed  in  water  at  the  same  time 
were  not  at  all  affected,  with  the  exception  of  one ; and  this  not 
until  8 hrs.  had  elapsed.  Hence  there  can  be  no  doubt  that  a 
highly  sensitive  leaf,  if  immersed  in  a solution,  so  that  all  the 
glands  are  enabled  to  absorb,  is  acted  on  by  of  a grain  of 
the  carbonate.  Assuming  that  the  leaf,  which  was  a large  one, 
and  which  had  all  its  tentacles  excepting  eight  inflected,  bore 
170  glands,  each  gland  could  have  absorbed  only  -^sV^  ^ 

grain  (’00024  mg.);  yet  this  sufficed  to  act  on  each  of  the  162 
tentacles  which  were  inflected.  But  as  only  four  out  of  the  above 
fourteen  leaves  were  plainly  affected,  this  is  nearly  the  mini- 
mum dose  which  is  efficient. 

Aggregation  of  the  Protoplasm  from  the  Action  of  Carbonate  of 
Ammonia, — I have  fully  described  in  the  third  chapter  the 
remarkable  effects  of  moderately  strong  doses  of  this  salt  in 
causing  the  aggregation  of  the  protoplasm  within  the  cells  of 
the  glands  and  tentacles ; and  here  my  object  is  merely  to  show 
what  small  doses  suffice.  A leaf  was  immersed  in  twenty 
minims  (1’183  ml.)  of  a solution  of  one  part  to  1750  of  water 


146 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


and  another  leaf  in  the  same  quantity  of  a solution  of  one  part 
to  3062 ; in  the  former  case  aggregation  occurred  in  4 m.,  in  the 
latter  in  11  m.  A leaf  was  then  immersed  in  twenty  minims  of 
a solution  of  one  part  to  4375  of  water,  so  that  it  received  2^  of 
a grain  (*27  mg.) ; in  5 m.  there  was  a slight  change  of  colour 
in  the  glands,  and  in  15  m.  small  spheres  of  protoplasm  were 
formed  in  the  cells  beneath  the  glands  of  all  the  tentacles.  In 
these  cases  there  could  not  be  a shadow  of  a doubt  about  the 
action  of  the  solution. 

A solution  was  then  made  of  one  part  to  5250  of  water,  and  I 
experimented  on  fourteen  leaves,  but  will  give  only  a few  of  the 
cases.  Eight  young  leaves  were  selected  and  examined  with 
care,  and  they  showed  no  trace  of  aggregation.  Four  of  these 
were  placed  in  a drachm  (3  * 549  ml.)  of  distilled  water ; and  four 
in  a similar  vessel,  with  a drachm  of  the  solution.  After  a time 
the  leaves  were  examined  under  a high  power,  being  taken  alter- 
nately from  the  solution  and  the  water.  The  first  leaf  was  taken 
out  of  the  solution  after  an  immersion  of  2 hrs.  40  m.,  and  the 
last  leaf  out  of  the  water  after  3 hrs.  50  m. ; the  examination 
lasting  for  1 hr.  40  m.  In  the  four  leaves  out  of  the  water  there 
was  no  trace  of  aggregation  except  in  one  specimen,  in  which  a 
very  few,  extremely  minute  spheres  of  protoplasm  were  present 
beneath  some  of  the  round  glands.  All  the  glands  were  trans- 
lucent and  red.  The  four  leaves  which  had  been  immersed  in 
the  solution,  besides  being  inflected,  presented  a widely  different 
appearance ; for  the  contents  of  the  cells  of  every  single  tentacle 
on  all  four  leaves  were  conspicuously  aggregated ; the  spheres 
and  elongated  masses  of  protoplasm  in  many  cases  extending 
halfway  down  the  tentacles.  All  the  glands,  both  those  of  the 
central  and  exterior  tentacles,  were  opaque  and  blackened ; and 
this  shows  that  all  had  absorbed  some  of  the  carbonate.  These 
four  leaves  were  of  very  nearly  the  same  size,  and  the  glands 
were  counted  on  one  and  found  to  be  167.  This  being  the  case, 
and  the  four  leaves  having  been  immersed  in  a drachm  of  the 
solution,  each  gland  could  have  received  on  an  average  only 
6 41^8  of  ^ grain  (*001009  mg.)  of  the  salt;  and  this  quantity 
sufficed  to  induce  within  a short  time  conspicuous  aggregation 
in  the  cells  beneath  all  the  glands. 

A vigorous  but  rather  small  red  leaf  was  placed  in  six 
minims  of  the  same  solution  (viz.  one  part  to  5250  of  water),  so 
that  it  received  of  a grain  ( *0675  mg.).  In  40  m.  the  glands 
appeared  rather  darker;  and  in  1 hr.  from  four  to  six  spheres 
of  protoplasm  were  formed  in  the  cells  beneath  the  glands  of 
all  the  tentacles.  I did  not  count  the  tentacles,  but  we  may 


Chap.  VII. 


CARBONATE  OF  AMMONIA. 


147 


safely  assume  that  there  were  at  least  140;  and  if  so,  each 
gland  could  have  received  only  the  t^^oo  ^ grain,  or 
*00048  mg. 

A weaker  solution  was  then  made  of  one  part  to  7000  of  water, 
and  four  leaves  were  immersed  in  it ; but  I will  give  only  one 
case.  A leaf  was  placed  in  ten  minims  of  this  solution ; after 
1 hr.  37  m.  the  glands  became  somewhat  darker,  and  the  cells 
beneath  all  of  them  now  contained  many  spheres  of  aggregated 
protoplasm.  This  leaf  received  of  a grain,  and  bore  166 
glands.  Each  gland  could,  therefore,  have  received  only 
of  a grain  (*000507  mg.)  of  the  carbonate. 

Two  other  experiments  are  worth  giving.  A leaf  was  im- 
mersed for  4 hrs.  15  m.  in  distilled  water,  and  there  was  no 
aggregation ; it  was  then  placed  for  1 hr.  15  m.  in  a little  solu- 
tion of  one  part  to  5250  of  water ; and  this  excited  well-marked 
aggregation  and  inflection.  Another  leaf,  after  having  been 
immersed  for  21  hrs.  15  m.  in  distilled  water,  had  its  glands 
blackened,  but  there  was  no  aggregation  in  the  cells  beneath 
them ; it  was  then  left  in  six  minims  of  the  same  solution,  and 
in  1 hr.  there  was  much  aggregation  in  many  of  the  tentacles ; 
in  2 hrs.  all  the  tentacles  (146  in  number)  were  affected — the 
aggregation  extending  down  for  a length  equal  to  half  or  the 
whole  of  the  glands.  It  is  extremely  improbable  that  these  two 
leaves  would  have  undergone  aggregation  if  they  had  been  left 
for  a little  longer  in  the  water,  namely  for  1 hr.  and  1 hr.  15  m., 
during  which  time  they  were  immersed  in  the  solution ; for  the 
process  of  aggregation  seems  invariably  to  supervene  slowly  and 
very  gradually  in  water. 

Summary  of  the  Results  with  Carhonate  of  Ammonia, — 
The  roots  absorb  the  solution,  as  shown  by  their  changed 
colour,  and  by  the  aggregation  of  the  contents  of  their 
cells.  The  vapour  is  absorbed  by  the  glands;  these 
are  blackened^  and  the  tentacles  are  inflected.  The 
glands  of  the  disc,  when  excited  by  a half-minim  drop 
(*0296  ml.),  containing  of  a grain  (*0675  mg.), 
transmit  a motor  impulse  to  the  exterior  tentacles, 
causing  them  to  bend  inwards.  A minute  drop,  con- 
taining -ttto-o  of  a grain  (*00445  mg.),  if  held  for  a 
few  seconds  in  contact  with  a gland,  soon  causes  the 
tentacle  bearing  it  to  be  inflected.  If  a leaf  is  left 


148 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


immersed  for  a few  hours  in  a solution,  and  a gland 
absorbs  the  c>f  a grain  (*00048  mg.),  its  colour 

becomes  darker,  though  not  actually  black ; and  the 
contents  of  the  cells  beneath  the  gland  are  plainly 
aggregated.  Lastly,  under  the  same  circumstances, 
the  absorption  by  a gland  of  the  q-q  ^ grain 
(*00024  mg.)  suffices  to  excite  the  tentacle  bearing  this 
gland  into  moyement. 


Nitrate  of  Ammonia. 

With  the  salt  I attended  only  to  the  inflection  of  the  leaves, 
for  it  is  far  less  efl&cient  than  the  carbonate  in  causing  aggrega- 
tion, although  considerably  more  potent  in  causing  inflection.  I 
experimented  with  half-minims  (*0296  ml .)  on  the  discs  of  fifty- 
two  leaves,  but  will  give  only  a few  cases.  A solution  of  one 
part  to  109  of  water  was  too  strong,  causing  little  inflection,  and 
after  24  hrs.  killing,  or  nearly  killing,  four  out  of  six  leaves 
which  were  thus  tried ; each  of  which  received  the  of  a grain 
(or  *27  mg.).  A solution  of  one  part  to  218  of  water  acted  most 
energetically,  causing  not  only  the  tentacles  of  all  the  leaves, 
but  the  blades  of  some,  to  be  strongly  inflected.  Fourteen 
leaves  were  tried  with  drops  of  a solution  of  one  part  to  875 
of  water,  so  that  the  disc  of  each  received  the  ygVo  ^ grain 
(*0337  mg.).  Of  these  leaves,  seven  were  very  strongly  acted  on, 
the  edges  being  generally  inflected ; two  were  moderately  acted 
on ; and  five  not  at  all.  1 subsequently  tried  three  of  these  latter 
five  leaves  with  urine,  saliva,  and  mucus,  but  they  wer^  only 
slightly  affected ; and  this  proves  that  they  were  not  in  an  active 
condition.  I mention  this  fact  to  show  how  necessary  it  is  to 
experiment  on  several  leaves.  Two  of  the  leaves,  which  were 
well  inflected,  re-expanded  after  51  hrs. 

In  the  following  experiment  I happened  to  select  very  sensi- 
tive leaves.  Half-minims  of  a solution  of  one  part  to  1094  of 
water  (i.e.  1 gr.  to  2|  oz.)  were  placed  on  the  discs  of  nine  leaves, 
so  that  each  received  the  ^ grain  ( 027  mg.).  Three  of 

them  had  their  tentacles  strongly  inflected  and  their  blades  curled 
inwards ; five  were  slightly  and  somewhat  doubtfully  affected, 
having  from  three  to  eight  of  their  exterior  tentacles  inflected : 
one  leaf  was  not  at  all  affected,  yet  was  afterwards  acted  on  by 
saliva.  In  six  of  these  cases,  a trace  of  action  was  perceptible  in 


Chap.  VII. 


NITKATE  OF  AMMONIA. 


149 


7 hrs.,  but  the  full  effect  was  not  produced  until  from  24  hrs.  tc 
30  hrs.  had  elapsed.  Two  of  the  leaves,  which  were  only  slightly 
inflected,  re-expanded  after  an  additional  interval  of  19  hrs. 

Half-minims  of  a rather  weaker  solution,  viz.  of  one  part  tc 
1312  of  water  (1  gr.  to  3 oz.)  were  tried  on  fourteen  leaves ; so  that 
each  received  ^Vo  ^ grain  (*0225  mg.),  instead  of,  as  in  the  last 
experiment,  of  a grain.  The  blade  of  one  was  plainly  in- 
flected, as  were  six  of  the  exterior  tentacles ; the  blade  of  a second 
was  slightly,  and  two  of  the  exterior  tentacles  well,  inflected,  all 
the  other  tentacles  being  curled  in  at  right  angles  to  the  disc ; 
three  other  leaves  had  from  five  to  eight  tentacles  inflected ; five 
others  only  two  or  three,  and  occasionally,  though  very  rarely, 
drops  of  pure  water  cause  this  much  action ; the  four  remaining 
leaves  were  in  no  way  affected,  yet  three  of  them,  when  subse- 
quently tried  with  urine,  became  greatly  inflected.  In  most  of 
these  cases  a slight  effect  was  perceptible  in  from  6 hrs.  to 
7 hrs.,  but  the  full  effect  was  not  produced  until  from  24  hrs. 
to  30  hrs.  had  elapsed.  It  is  obvious  that  we  have  here  reached 
very  nearly  the  minimum  amount,  which,  distributed  between 
the  glands  of  the  disc,  acts  on  the  exterior  tentacles  ; these 
having  themselves  not  received  any  of  the  solution. 

In  the  next  place,  the  viscid  secretion  round  three  of  the 
exterior  glands  was  touched  with  the  same  little  drop  of  a 
minim)  of  a solution  of  one  part  to  437  of  water ; and  after  an 
interval  of  2 hrs.  50  m.  all  three  tentacles  were  well  inflected. 
Each  of  these  glands  could  have  received  only  the  ^ 

grain,  or  *00225  mg.  A little  drop  of  the  same  size  and  strength 
was  also  applied  to  four  other  glands,  and  in  I hr.  two  became 
inflected,  whilst  the  other  two  never  moved.  We  here  see,  as  in 
the  case  of  the  half-minims  placed  on  the  discs,  that  the  nitrate 
of  ammonia  is  more  potent  in  causing  inflection  than  the  car- 
bonate ; for  minute  drops  of  the  latter  salt  of  this  strength  pro- 
duced no  effect.  I tried  minute  drops  of  a still  weaker  solution 
of  the  nitrate,  viz.  one  part  to  875  of  water,  on  twenty-one 
glands,  but  no  effect  whatever  was  produced,  except  perhaps  in 
one  instance. 

Sixty-three  leaves  were  immersed  in  solutions  of  various 
strengths ; other  leaves  being  immersed  at  the  same  time  in  the 
same  pure  water  used  in  making  the  solutions.  The  results  are 
so  remarkable,  though  less  so  than  with  phosphate  of  ammonia, 
that  I must  describe  the  experiments  in  detail,  but  I will  give 
only  a few.  In  speaking  of  the  successive  periods  when 
inflection  occurred,  I always  reckon  from  the  time  of  first 
immersion. 


150 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


Having  made  some  preliminary  trials  as  a guide,  five  leaves 
were  placed  in  the  same  little  vessel  in  thirty  minims  of  a solu- 
tion of  one  part  of  the  nitrate  to  7875  of  water  (1  gr.  to  18  oz.); 
and  this  amount  of  fluid  just  sujficed  to  cover  them.  After 
2 hrs.  10  m.  three  of  the  leaves  were  considerably  inflected,  and 
the  other  two  moderately.  The  glands  of  all  became  of  so  dark 
a red  as  almost  to  deserve  to  be  called  black.  After  8 hrs.  four 
of  the  leaves  had  aU  their  tentacles  more  or  less  inflected ; whilst 
the  fifth,  which  I then  perceived  to  be  an  old  leaf,  had  only  thirty 
tentacles  inflected.  Next  morning,  after  23  hrs.  40  m.,  all  the 
leaves  were  in  the  same  state,  excepting  that  the  old  leaf  had  a 
few  more  tentacles  inflected.  Five  leaves  which  had  been  placed 
at  the  same  time  in  water  were  observed  at  the  same  intervals 
of  time ; after  2 hrs.  10  m.  two  of  them  had  four,  one  had  seven, 
one  had  ten,  of  the  long-headed  marginal  tentacles,  and  the 
fifth  had  four  round-headed  tentacles,  inflected.  After  8 hrs. 
there  was  no  change  in  these  leaves,  and  after  24  hrs.  all  the 
marginal  tentacles  had  re-expanded ; but  in  one  leaf,  a dozen,  and 
in  a second  leaf,  half  a dozen,  submarginal  tentacles  had  become 
inflected.  As  the  glands  of  the  five  leaves  in  the  solution  were 
simultaneously  darkened,  no  doubt  they  had  all  absorbed  a nearly 
equal  amount  of  the  salt : and  as  of  a grain  was  given  to  the 
five  leaves  together,  each  got  of  a grain  (*045  mg.).  I did 
not  count  the  tentacles  on  these  leaves,  which  were  moderately 
fine  ones,  but  as  the  average  number  on  thirty-one  leaves  was 
192,  it  would  be  safe  to  assume  that  each  bore  on  an  average  at 
least  160.  If  so,  each  of  the  darkened  glands  could  have 
received  only  230^4.00  ^ grain  of  the  nitrate ; and  this  caused 

the  inflection  of  a great  majority  of  the  tentacles. 

This  plan  of  immersing  several  leaves  in  the  same  vessel 
is  a bad  one,  as  it  is  impossible  to  feel  sure  that  the  more 
vigorous  leaves  do  not  rob  the  weaker  ones  of  their  share  of 
the  salt.  The  glands,  moreover,  must  often  touch  one  another 
or  the  sides  of  the  vessel,  and  movement  may  have  been  thus 
excited;  but  the  corresponding  leaves  in  water,  which  were 
little  inflected,  though  rather  more  so  than  commonly  occurs, 
were  exposed  in  an  almost  equal  degree  to  these  same  sources 
of  error.  I will,  therefore,  give  only  one  other  experiment  made 
in  this  manner,  though  many  were  tried  and  all  confirmed 
the  foregoing  and  following  results.  Four  leaves  were  placed 
in  forty  minims  of  a solution  of  one  part  to  10,500  of  water; 
and  assuming  that  they  absorbed  equally,  each  leaf  received 
of  a grain  (*0562  mg.).  After  1 hr.  20  m.  many  of  the 
tentacles  on  all  four  leaves  were  somewhat  inflected.  After 


Chap.  VII. 


NITRATE  OF  AMMONIA. 


151 


5 hrs.  30  m.  two  leaves  had  all  their  tentacles  inflected;  a 
third  leaf  all  except  the  extreme  marginals,  which  seemed  old 
and  torpid ; and  the  fourth  a large  number.  After  21  hrs. 
every  single  tentacle,  on  all  four  leaves,  was  closely  inflected. 
Of  the  four  leaves  placed  at  the  same  time  in  water,  one  had, 
after  5 hrs.  45  m.,  five  marginal  tentacles  inflected ; a second, 
ten ; a third,  nine  marginals  and  submarginals ; and  the  fourth, 
twelve,  chiefly  submarginals,  inflected.  After  21  hrs.  all  these 
marginal  tentacles  re-expanded,  but  a few  of  the  submarginals 
on  two  of  the  leaves  remained  slightly  curved  inwards.  The 
contrast  was  wonderfully  great  between  these  four  leaves  in 
water  and  those  in  the  solution,  the  latter  having  every  one  of 
their  tentacles  closely  inflected.  Making  the  moderate  assump- 
tion that  each  of  these  leaves  bore  160  tentacles,  each  gland 
could  have  absorbed  only  yg  JsTo  ^ grain  (‘000351  mg.). 
This  experiment  was  repeated  on  three  leaves  with  the  same 
relative  amount  of  the  solution ; and  after  6 hrs.  15  m.  all  the 
tentacles  except  nine,  on  all  three  leaves  taken  together,  were 
closely  inflected.  In  this  case  the  tentacles  on  each  leaf  were 
counted,  and  gave  an  average  of  162  per  leaf. 

The  following  experiments  w’ere  tried  during  the  summer  of 
1873,  by  placing  the  leaves,  each  in  a separate  watch-glass  and 
pouring  over  it  thirty  minims  (1*775  ml.)  of  the  solution ; other 
leaves  being  treated  in  exactly  the  same  manner  with  the 
doubly  distilled  water  used  in  making  the  solutions.  The 
trials  above  given  were  made  several  years  before,  and  when  I 
read  over  my  notes,  I could  not  believe  in  the  results;  so  I 
resolved  to  begin  again  with  moderately  strong  solutions.  Six 
leaves  were  first  immersed,  each  in  thirty  minims  of  a solution  of 
one  part  of  the  nitrate  to  8750  of  water  (1  gr.  to  20  oz.),  so  that 
each  received  of  a grain  ( 2025  mg.).  Before  30  m.  had 
elapsed,  four  of  these  leaves  were  immensely,  and  two  of  them 
moderately,  inflected.  The  glands  were  rendered  of  a dark 
red.  The  four  corresponding  leaves  in  water  were  not  at  all 
affected  until  6 hrs.  had  elapsed,  and  then  only  the  short  ten- 
tacles on  the  borders  of  the  disc;  and  their  inflection,  as 
previously  explained,  is  never  of  any  significance. 

Four  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  to  17,500  of  water  (1  gr.  to  40  oz.),  so  that  each 
received  of  a grain  (*101  mg.;;  and  in  less  than  45  m.  three 
of  them  had  all  their  tentacles,  except  from  four  to  ten,  inflected; 
the  blade  of  one  being  inflected  after  6 hrs.,  and  the  blade  of  a 
second  after  21  hrs.  The  fourth  leaf  was  not  at  all  affected. 
The  glands  of  none  were  darkened.  Of  the  corresponding  leaves 


152 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


in  water,  only  one  had  any  of  its  exterior  tentacles,  namely  five, 
inflected ; after  6 hrs.  in  one  case,  and  after  21  hrs.  in  two  other 
cases,  the  short  tentacles  on  the  borders  of  the  disc  formed  a 
ring,  in  the  nsnal  manner. 

Four  leaves  were  immersed,  each  in  thirty  minims  of  a solution 
of  one  part  to  43,750  of  water  (1  gr.  to  100  oz.),  so  that  each  leaf 
got  of  a grain  (-0405  mg.).  Of  these,  one  was  much  in- 
flected in  8 m.,  and  after  2 hrs.  7 m.  had  all  the  tentacles, 
except  thirteen,  inflected.  The  second  leaf,  after  10  m.,  had  all 
except  three  inflected.  The  third  and  fourth  were  hardly  at  all 
affected,  scarcely  more  than  the  corresponding  leaves  in  water. 
Of  the  latter,  only  one  was  affected,  this  having  two  tentacles 
inflected,  with  those  on  the  outer  parts  of  the  disc  forming  a 
ring  in  the  usual  manner.  In  the  leaf  which  had  all  its  ten- 
tacles except  three  inflected  in  10  m.,  each  gland  (assuming  that 
the  leaf  bore  160  tentacles)  could  have  absorbed  only  stV^ 
a grain,  or  *000258  mg. 

Four  leaves  were  separately  immersed  as  before  in  a solution 
of  one  part  to  131,250  of  water  (1  gr.  to  300  oz.),  so  that  each 
received  ygVo  ^ or  *0135  mg.  After  50  m.  one  leaf  had 
all  its  tentacles  except  sixteen,  and  after  8 hrs.  20  m.  all  but 
fourteen,  inflected.  The  second  leaf,  after  40  m.,  had  all  but 
twenty  inflected;  and  after  8 hrs.  10  m.  began  to  re- expand. 
The  third,  in  3 hrs.  had  about  half  its  tentacles  inflected,  which 
began  to  re-expand  after  8 hrs.  15  m.  The  fourth  leaf,  after 
3 hrs.  7 m.,  had  only  twenty-nine  tentacles  more  or  less  in- 
flected. Thus  three  out  of  the  four  leaves  were  strongly  acted 
on.  It  is  clear  that  very  sensitive  leaves  had  been  accidentally 
selected.  The  day  moreover  was  hot.  The  four  corresponding 
leaves  in  water  were  likewise  acted  on  rather  more  than  is  usual; 
for  after  3 hrs.  one  had  nine  tentacles,  another  four,  and 
another  two,  and  the  fourth  none,  inflected.  With  respect  to 
the  leaf  of  which  all  the  tentacles,  except  sixteen,  were  inflected 
after  50  m.,  each  gland  (assuming  that  the  leaf  bore  160  ten- 
tacles) could  have  absorbed  only  -^^oo  ^ grain  (*0000937 

mg.),  and  this  appears  to  be  about  the  least  quantity  of  the 
nitrate  which  suffices  to  induce  the  inflection  of  a single  tentacle. 

As  negative  results  are  important  in  confirming  the  foregoing 
positive  ones,  eight  leaves  were  immersed  as  before,  each  in  thirty 
minims  of  a solution  of  one  part  to  175,000  of  water  (1  gr.  to 
400  oz.),  so  that  each  received  only  of  a grain  (*0101  mg.). 
This  minute  quantity  produced  a slight  effect  on  only  four  of 
the  eight  leaves.  One  had  fifty-six  tentacles  inflected  after  2 hrs. 
13  m. ; a second,  twenty-six  inflected,  or  sub-inflected,  after 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


153 


38  m.;  a third,  eighteen  inflected,  after  1 hr.;  and  a fourth, 
ten  inflected,  after  35  m.  The  four  other  leaves  were  not  in 
the  least  affected.  Of  the  eight  corresponding  leaves  in  water, 
one  had,  after  2 hrs.  10  m.,  nine  tentacles,  and  four  others  from 
one  to  four  long-headed  tentacles,  inflected ; the  remaining  three 
being  unaffected.  Hence,  the  ^ grain  given  to  a sensi- 

tive leaf  during  warm  weather  perhaps  produces  a slight  effect; 
but  we  must  bear  in  mind  that  occasionally  water  causes  as 
great  an  amount  of  inflection  as  occurred  in  this  last  ex- 
periment. 

Summary  of  the  Besults  ivith  Nitrate  of  Ammonia. — 
The  glands  of  the  disc,  when  excited  by  a half-minim 
drop  (*0296  ml.),  containing  4V0  ^ grain  of  the 

nitrate  (*027  mg.),  transmit  a motor  impulse  to  the 
exterior  tentacles,  causing  them  to  bend  inwards.  A 
minute  drop,  containing  ] o q-  of  a grain  (*00225  mg.), 
if  held  for  a few  seconds  in  contact  with  a gland, 
causes  the  tentacle  bearing  this  gland  to  be  inflected 
If  a leaf  is  left  immersed  for  a few  hours,  and  some- 
times for  only  a few  minutes,  in  a solution  of  such 
strength  that  each  gland  can  absorb  only  the  -g-g-A-o  o 
of  a grain  (*0000937  mg.),  this  small  amount  is 
enough  to  excite  each  tentacle  into  movement,  and 
it  becomes  closely  inflected. 


Phosphate  of  Ammonia. 

This  salt  is  more  powerful  than  the  nitrate,  even 
in  a greater  degree  than  the  nitrate  is  more  powerful 
than  the  carbonate.  This  is  shown  by  weaker  solu- 
tions of  the  phosphate  acting  when  dropped  on  the 
discs,  or  applied  to  the  glands  of  the  exterior  ten- 
tacles, or  when  leaves  are  immersed.  The  difference 
in  the  power  of  these  three  salts,  as  tried  in  three 
different  ways,  supports  the  results  presently  to  be 


154 


DROSERA  ROTUNDIFOLIA. 


Chap.  Vn. 


given,  which  are  so  surprising  that  their  credi- 
bility requires  every  kind  of  support.  In  1872  I 
experimented  on  twelve  immersed  leaves,  giving  each 
only  ten  minims  of  a solution;  but  this  was  a bad 
method,  for  so  small  a quantity  hardly  covered  them. 
None  of  these  experiments  will,  therefore,  be  given, 
though  they  indicate  that  excessively  minute  doses 
are  efficient.  When  I read  over  my  notes,  in  1873, 
I entirely  disbelieved  them,  and  determined  to  mako 
another  set  of  experiments  with  scrupulous  care,  on 
the  same  plan  as  those  made  with  the  nitrate ; namely 
by  placing  leaves  in  watch-glasses,  and  pouring  over 
each  thirty  minims  of  the  solution  under  trial,  treat- 
ing at  the  same  time  and  in  the  same  manner  other 
leaves  with  the  distilled  water  used  in  making  the 
solutions.  During  1873,  seventy-one  leaves  were  thus 
tried  in  solutions  of  various  strengths,  and  the  same 
number  in  water.  Notwithstanding  the  care  taken 
and  the  number  of  the  trials  made,  when  in  the 
following  year  I looked  merely  at  the  results,  without 
reading  over  my  observations,  I again  thought  that 
there  must  have  been  some  error,  and  thirty-five  fresh 
trials  were  made  with  the  weakest  solution ; but 
the  results  were  as  plainly  marked  as  before.  Al- 
together, 106  carefully  selected  leaves  were  tried, 
both  in  water  and  in  solutions  of  the  phosphate. 
Hence,  after  the  most  anxious  consideration,  I can 
entertain  no  doubt  of  the  substantial  accuracy  of  my 
results. 

Before  giving  my  experiments,  it  may  be  well  to  premise  that 
crystallised  phosphate  of  ammonia,  such  as  I used,  contains 
35*33  per  cent,  of  water  of  crystallisation;  so  that  in  all  the 
following  trials  the  efficient  elements  formed  only  64*67  per 
cent,  of  the  salt  used. 

Extremely  minute  particles  of  the  dry  phosphate  were  placed 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


155 


with  the  point  of  a needle  on  the  secretion  surrounding  several 
glands.  These  poured  forth  much  secretion,  were  blackened, 
and  ultimately  died;  but  the  tentacles  moved  only  slightly. 
The  dose,  small  as  it  was,  evidently  was  too  great,  and  the 
result  was  the  same  as  with  particles  of  the  carbonate  of 
ammonia. 

Half-minims  of  a solution  of  one  part  to  437  of  water  were 
placed  on  the  discs  of  three  leaves  and  acted  most  energetically, 
causing  the  tentacles  of  one  to  be  inflected  in  15  m.,  and* 
the  blades  of  all  three  to  be  much  curved  inwards  in  2 hrs. 
15  m.  Similar  drops  of  a solution  of  one  part  to  1312  of  water, 
(1  gr.  to  3 oz.)  were  then  placed  on  the  discs  of  five  leaves, 
so  that  each  received  the  ^ grain  (*0225  mg.).  After 

8 hrs.  the  tentacles  of  four  of  them  were  considerably  inflected, 
and  after  24  hrs.  the  blades  of  three.  After  48  hrs.  all  five 
were  almost  fully  re-expanded.  I may  mention  with  respect 
to  one  of  these  leaves,  that  a drop  of  water  had  been  left 
during  the  previous  24  hrs.  on  its  disc,  but  produced  no  effect ; 
and  that  this  was  hardly  dry  when  the  solution  was  added. 

Similar  drops  of  a solution  of  one  part  to  1750  of  water  (1  gr. 
to  4 oz.)  were  next  placed  on  the  discs  of  six  leaves ; so  that 
each  received  ^ grain  (*0169  mg.) ; after  8 hrs.  three  of 

them  had  many  tentacles  and  their  blades  inflected ; two  others 
had  only  a few  tentacles  slightly  inflected,  and  the  sixth  was 
not  at  all  affected.  After  24  hrs.  most  of  the  leaves  had  a few 
more  tentacles  inflected,  but  one  had  begun  to  re-expand.  We 
thus  see  that  with  the  more  sensitive  leaves  the  g of  a grain, 
absorbed  by  the  central  glands,  is  enough  to  make  many  of  the 
exterior  tentacles  and  the  blades  bend,  whereas  the  of  a 
grain  of  the  carbonate  similarly  given  produced  no  effect ; and 
2 sVo  of  ^ grain  of  the  nitrate  was  only  just  sufficient  to  produce 
a well-marked  effect. 

A minute  drop,  about  equal  to  Jq  of  a minim,  of  a solution  of 
one  part  of  the  phosphate  to  875  of  water,  was  applied  to  the 
secretion  on  three  glands,  each  of  which  thus  received  only 
g-yjyo  of  a grain  (*00112  mg.),  and  all  three  tentacles  became 
inflected.  Similar  drops  of  a solution  of  one  part  to  1312  of 
water  (1  gr.  to  3 oz.)  were  now  tried  on  three  leaves;  a drop 
being  applied  to  four  glands  on  the  same  leaf.  On  the  first 
leaf,  three  of  the  tentacles  became  slightly  inflected  in  6 m.,  and 
re-expanded  after  8 hrs.  45  m.  On  the  second,  two  tentacles 
became  sub-inflected  in  12  m.  And  on  the  third  all  four  ten- 
tacles were  decidedly  inflected  in  12  m. ; they  remained  so  for 
8 hrs.  30  m.,  but  by  the  next  morning  were  fully  re-expanded. 


156 


DKOSERA  ROTUNDIFOLIA. 


Chap.  YII. 


In  this  latter  case  each  gland  could  have  received  only  the 
^ Q-Q-  (or  *000563  mg.)  of  a grain.  Lastly,  similar  drops  of  a 
solution  of  one  part  to  1750  of  water  (1  gr.  to  4oz.)  were  tried  on 
five  leaves ; a drop  being  applied  to  four  glands  on  the  same 
leaf.  The  tentacles  on  three  of  these  leaves  were  not  in  the 
least  affected ; on  the  fourth  leaf,  two  became  inflected ; whilst 
on  the  fifth,  which  happened  to  be  a very  sensitive  one,  all  four 
tentacles  were  plainly  inflected  in  6 hrs.  15  m. ; but  only  one  re- 
mained inflected  after  24  hrs.  I should,  however,  state  that  in 
this  case  an  unusually  large  drop  adhered  to  the  head  of  the 
pin.  Each  of  these  glands  could  have  received  very  little  more 
than  i^sVoo  ^ grain  (or  *000423);  but  this  small  quantity 
sufficed  to  cause  inflection.  We  must  bear  in  mind  that  these 
drops  were  applied  to  the  viscid  secretion  for  only  from  10  to 
15  seconds,  and  we  have  good  reason  to  believe  that  all  the 
phosphate  in  the  solution  would  not  be  diffused  and  absorbed  in 
this  time.  We  have  seen  under  the  same  circumstances  that  the 
absorption  by  a gland  of  yoIoo  ^ grain  of  the  carbonate,  and 
of  Yfloo  ^ grain  of  the  nitrate,  did  not  cause  the  tentacle  bear- 
ing the  gland  in  question  to  be  inflected ; so  that  here  again  the 
phosphate  is  much  more  powerful  than  the  other  two  salts. 

We  will  now  turn  to  the  106  experiments  with  immersed 
leaves.  Having  ascertained  by  repeated  trials  that  moderately 
strong  solutions  were  highly  efficient,  I commenced  with  sixteen 
leaves,  each  placed  in  thirty  minims  of  a solution  of  one  part 
to  43,750  of  water  (1  gr.  to  100  oz.);  so  that  each  received 
of  a grain,  or  *04058  mg.  Of  these  leaves,  eleven  had 
nearly  all  or  a great  number  of  their  tentacles  inflected  in 
1 hr.,  and  the  twelfth  leaf  in  3 hrs.  One  of  the  eleven  had 
every  single  tentacle  closely  inflected  in  50  m.  Two  leaves  out 
of  the  sixteen  were  only  moderately  affected,  yet  more  so 
than  any  of  those  simultaneously  immersed  in  water ; and  the 
remaining  two,  which  were  pale  leaves,  were  hardly  at  all 
affected.  Of  the  sixteen  corresponding  leaves  in  water,  one 
had  nine  tentacles,  another  six,  and  two  others  two  tentacles 
inflected,  in  the  course  of  5 hrs.  So  that  the  contrast  ir 
appearance  between  the  two  lots  was  extremely  great. 

Eighteen  leaves  were  immersed,  each  in  thirty  minims  of  a 
solution  of  one  part  to  87,500  of  water  (1  gr.  to  200  oz.),  so 
that  each  received  ^ grain  (*0202  mg.).  Fourteen  ol 

these  were  strongly  inflected  within  2 hrs.,  and  some  of  them 
within  15  m. ; three  out  of  the  eighteen  were  only  slightly 
affected,  having  twenty-one,  nineteen,  and  twelve  tentacles  in- 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


157 


fleeted ; and  one  was  not  at  all  acted  on.  By  an  accident  only 
fifteen,  instead  of  eighteen,  leaves  were  immersed  at  the  same 
time  in  water ; these  were  observed  for  24  hrs. ; one  had  six, 
another  four,  and  a third  two,  of  their  outer  tentacles  inflected ; 
the  remainder  being  quite  unaffected. 

The  next  experiment  was  tried  under  very  favourable  circum- 
stances, fort  he  day  (July  8)  was  very  warm,  and  I happened 
to  have  unusually  fine  leaves.  Five  were  immersed  as  before  in 
a solution  of  one  part  to  131,250  of  water  (1  gr.  to  300  oz.),  sc 
that  each  received  ^ grain,  or  *0135  mg.  After  an 

immersion  of  25  m.  ail  five  leaves  were  much  inflected.  After 
1 hr.  25  m.  one  leaf  had  all  but  eight  tentacles  inflected;  the 
second,  all  but  three ; the  third,  all  but  five  ; the  fourth,  all  but 
twenty-three;  the  fifth,  on  the  other  hand,  never  had  more 
than  twenty-four  inflected.  Of  the  corresponding  five  leaves  in 
water,  one  had  seven,  a second  two,  a third  ten,  a fourth  one, 
and  a fifth  none  inflected.  Let  it  be  observed  what  a contrast 
is  presented  between  these  latter  leaves  and  those  in  the  solu- 
tion. I counted  the  glands  on  the  second  leaf  in  the  solution, 
and  the  number  was  217 ; assuming  that  the  three  tentacles 
which  did  not  become  inflected  absorbed  nothing,  we  find 
that  each  of  the  214  remaining  glands  could  have  absorbed 
io~2  7 2o'o  ^ grain,  or  *0000631  mg.  The  third  leaf  bore 
236  glands,  and  subtracting  the  five  which  did  not  become  in- 
flected, each  of  the  remaining  231  glands  could  have  absorbed 
oiily  110  8 8 0 0 ^ grain  (or  *0000584  mg.),  and  this  amount 

sufficed  to  cause  the  tentacles  to  bend. 

Twelve  leaves  were  tried  as  before  in  a solution  of  one  part  to 
175,000  of  water  (1  gr.  to  400  oz.),  so  that  each  leaf  received 
of  a grain  (*0101  mg.).  My  plants  were  not  at  the  time  in 
a good  state,  and  many  of  the  leaves  were  young  and  pale. 
Nevertheless,  two  of  them  had  all  their  tentacles,  except  three 
or  four,  closely  inflected  in  under  1 hr.  Seven  were  con- 
siderably affected,  some  within  1 hr.,  and  others  not  until  3 hrs., 
4 hrs.  30  m.,  and  8 hrs.  had  elapsed;  and  this  slow  action 
may  be  attributed  to  the  leaves  being  young  and  pale.  Of 
these  nine  leaves,  four  had  their  blades  well  inflected,  and  a 
fifth  slightly  so.  The  three  remaining  leaves  were  not  affected. 
With  respect  to  the  twelve  corresponding  leaves  in  water,  not 
one  had  its  blade  inflected;  after  from  1 to  2 hrs.  one  had 
thirteen  of  its  outer  tentacles  inflected ; a second  six,  and  four 
others  either  one  or  two  inflected.  After  8 hrs.  the  outer 
tentacles  did  not  become  more  inflected ; whereas  this  occurred 
with  the  leaves  in  the  solution.  I record  in  my  notes  that 


158 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII 


after  the  8 hrs.  it  was  impossible  to  compare  the  two  lots,  and 
doubt  for  an  instant  the  power  of  the  solution. 

Two  of  the  above  leaves  in  the  solution  had  all  their  tentacles, 
except  three  and  four,  inflected  within  an  hour.  I counted  their 
glands,  and,  on  the  same  principle  as  before,  each  gland  on  one 
leaf  could  have  absorbed  only  xreisoo^  the  other  leaf 

only  147^0-^t  of  a grain  of  the  phosphate. 

Twenty  leaves  were  immersed  in  the  usual  manner,  each  in 
thirty  minims  of  a solution  of  one  part  to  218,750  of  water  (1  gr. 
to  500  oz.).  So  many  leaves  were  tried  because  I was  then 
under  the  false  impression  that  it  was  incredible  that  any 
weaker  solution  could  produce  an  effect.  Each  leaf  received 
of  a grain,  or  *0081  mg.  The  first  eight  leaves  which  I 
tried  both  in  the  solution  and  in  water  were  either  young  and 
pale  or  too  old ; and  the  weather  was  not  hot.  They  were  hardly 
at  all  affected ; nevertheless,  it  would  be  unfair  to  exclude  them. 
I then  waited  until  I got  eight  pairs  of  fine  leaves,  and  the 
weather  was  favourable ; the  temperature  of  the  room  where  the 
leaves  were  immersed  varying  from  75°  to  81°  (23°-8  to  27°*2 
Cent.).  In  another  trial  with  four  pairs  (included  in  the  above 
twenty  pairs),  the  temperature  in  my  room  was  rather  low, 
about  60°  (15°*5  Cent.) ; but  the  plants  had  been  kept  for  several 
days  in  a very  warm  greenhouse  and  thus  rendered  extremely 
sensitive.  Special  precautions  were  taken  for  this  set  of  experi- 
ments; a chemist  weighed  for  me  a grain  in  an  excellent 
balance ; and  fresh  water,  given  me  by  Professor  Frankland,  was 
carefully  measured.  The  leaves  were  selected  from  a large 
number  of  plants  in  the  following  manner : the  four  finest  wero 
immersed  in  water,  and  the  next  four  finest  in  the  solution,  and 
so  on  till  the  twenty  pairs  were  complete.  The  water  specimens 
were  thus  a little  favoured,  but  they  did  not  undergo  more  in- 
flection than  in  the  previous  cases,  comparatively  with  those 
in  the  solution. 

Of  the  twenty  leaves  in  the  solution,  eleven  became  inflected 
within  40  m. ; eight  of  them  plainly  and  three  rather  doubt- 
fully ; but  the  latter  had  at  least  twenty  of  their  outer  tentacles 
inflected.  Owing  to  the  weakness  of  the  solution,  inflection 
occurred,  except  in  No.  1,  much  more  slowly  than  in  the  pre- 
vious trials.  The  condition  of  the  eleven  leaves  which  were 
considerably  inflected  will  now  be  given  at  stated  intervals, 
always  reckoning  from  the  time  of  immersion  : — 

(1)  After  only  8 m.  a large  number  of  tentacles  inflected, 
and  after  17  m.  all  but  fifteen;  after  2 hrs.  all  but  eight  in- 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


159 


fleeted,  or  plainly  snb-inflected.  After  4 hrs.  the  tentacles 
began  to  re-expand,  and  such  prompt  re-expansion  is  unusual ; 
after  7 hrs.  30  m.  they  were  almost  fully  re-expanded. 

(2)  After  39  m.  a large  number  of  tentacles  inflected ; after 
2 hrs.  18  m.  all  but  twenty-five  inflected ; after  4 hrs.  17  m.  all 
but  sixteen  inflected.  The  leaf  remained  in  this  state  for  many 
hours. 

(3)  After  12  m.  a considerable  amount  of  inflection;  after 
4 hrs.  all  the  tentacles  inflected  except  those  of  the  two  outer 
rows,  and  the  leaf  remained  in  this  state  for  some  time ; after 

23  hrs.  began  to  re-expand. 

(4)  After  40  m.  much  inflection ; after  4 hrs.  13  m.  fully  half 
the  tentacles  inflected ; after  23  hrs.  still  slightly  inflected. 

(5)  After  40  m.  much  inflection ; after  4 hrs.  22  m.  fully  half 
the  tentacles  inflected ; after  23  hrs.  still  slightly  inflected. 

(6)  After  40  m.  some  inflection;  after  2 hrs.  18  m.  about 
twenty-eight  outer  tentacles  inflected ; after  5 hrs.  20  m.  about  a 
third  of  the  tentacles  inflected ; after  8 hrs.  much  re-expanded. 

(7)  After  20  m.  some  inflection ; after  2 hrs.  a considerable 
number  of  tentacles  inflected;  after  7 hrs.  45  m.  began  to 
re-expand. 

(8)  After  38  m.  twenty-eight  tentacles  inflected ; after  3 hrs. 
45  m.  thirty-three  inflected,  with  most  of  the  submarginal 
tentacles  sub-inflected  ; continued  so  for  two  days,  and  then 
partially  re-expanded. 

(9)  After  38  m.  forty-two  tentacles  inflected;  after  3 hrs. 
12  m.  sixty-six  inflected  or  sub-inflected ; after  6 hrs.  40  m.  all 
but  twenty-four  inflected  or  sub-inflected ; after  9 hrs.  40  m.  all 
but  seventeen  inflected ; after  24  hrs.  all  but  four  inflected  or 
sub-inflected,  only  a few  being  closely  inflected;  after  27  hrs. 
40  m.  the  blade  inflected.  The  leaf  remained  in  this  state  for 
two  days,  and  then  began  to  re-expand. 

(10)  After  38  m.  twenty-one  tentacles  inflected ; after  3 hrs. 
12  m.  forty- six  tentacles  inflected  or  sub-inflected;  after  6 hrs. 
10  m.  all  but  seventeen  inflected,  though  none  closely;  after 

24  hrs.  every  tentacle  slightly  curved  inwards  ; after  27  hrs. 
40  m.  blade  strongly  inflected,  and  so  continued  for  two  days, 
and  then  the  tentacles  and  blade  very  slowly  re-expanded. 

(11)  This  fine  dark  red  and  rather  old  leaf,  though  not  very 
large,  bore  an  extraordinary  number  of  tentacles  (viz.  252),  and 
behaved  in  an  anomalous  manner.  After  6 hrs.  40  m.  only  the 
short  tentacles  round  the  outer  part  of  the  disc  were  inflected, 
forming  a ring,  as  so  often  occurs  in  from  8 to  24  hrs.  with 
leaves  both  in  water  and  the  weaker  solutions.  But  after  9 hrs. 

8 


160 


DKOSERA  ROTUNDIFOLIA. 


Chap.  VII. 


10  m.  all  the  outer  tentacles  except  twenty-five  were  inflected, 
as  was  the  blade  in  a strongly  marked  manner.  After  24  hrs. 
every  tentacle  except  one  was  closely  inflected,  and  the  blade 
was  completely  doubled  over.  Thus  the  leaf  remained  for  two 
days,  when  it  began  to  re-expand.  1 may  add  that  the  three 
latter  leaves  (Nos.  9,  10,  and  11)  were  still  somewhat  inflected 
after  three  days.  The  tentacles  in  but  few  of  these  eleven  leaves 
became  closely  inflected  within  so  short  a time  as  in  the  pre- 
vious experiments  with  stronger  solutions. 

We  will  now  turn  to  the  twenty  corresponding  leaves  in  water. 
Nine  had  none  of  their  outer  tentacles  inflected;  nine  others 
had  from  one  to  three  inflected;  and  these  re-expanded  after 
8 hrs.  The  remaining  two  leaves  were  moderately  affected ; one 
having  six  tentacles  inflected  in  34  m. ; the  other  twenty-three 
inflected  in  2 hrs.  12  m. ; and  both  thus  remained  for  24  hrs. 
None  of  these  leaves  had  their  blades  inflected.  So  that  the  con- 
trast between  the  twenty  leaves  in  water  and  the  twenty  in  the 
solution  was  very  great,  both  within  the  first  hour  and  after 
from  8 to  12  hrs.  had  elapsed. 

Of  the  leaves  in  the  solution,  the  glands  on  leaf  No.  1,  which 
in  2 hrs.  had  all  its  tentacles  except  eight  inflected,  were 
counted  and  found  to  be  202.  Subtracting  the  eight,  each  gland 
could  have  received  only  the  ^ grain  (*0000411  mg.) 

of  the  phosphate.  Leaf  No.  9 had  213  tentacles,  all  of  which, 
with  the  exception  of  four,  were  inflected  after  24  hrs.,  but 
none  of  them  closely ; the  blade  was  also  inflected ; each  gland 
could  have  received  only  the  Tfiriwoo  ^ grain,  or  *0000387 
mg.  Lastly,  leaf  No.  11,  which  had  after  24  hrs.  all  its  ten- 
tacles, except  one,  closely  inflected,  as  well  as  the  blade,  bore 
the  unusually  large  number  of  252  tentacles ; and  on  the  same 
principle  as  before,  each  gland  could  have  absorbed  only  the 
of  a grain,  or  *0000322  mg. 

With  respect  to  the  following  experiments,  I must  premise 
that  the  leaves,  both  those  placed  in  the  solutions  and  in  water, 
were  taken  from  plants  which  had  been  kept  in  a very  warm 
greenhouse  during  the  winter.  They  were  thus  rendered  ex- 
tremely sensitive,  as  was  shown  by  water  exciting  them  much 
more  than  in  the  previous  experiments.  Before  giving  my 
observations,  it  may  be  well  to  remind  the  reader  that,  judging 
from  thirty-one  fine  leaves,  the  average  number  of  tentacles  is 
192,  and  that  the  outer  or  exterior  ones,  the  movements  of 
which  are  alone  significant,  are  to  the  short  ones  on  the  disc  in 
the  proportion  of  about  sixteen  to  nine. 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


161 


Four  leaves  were  immersed  as  before,  each  in  thirty  minims 
of  a solution  of  one  part  to  328,125  of  water  (1  gr.  to  750  oz.). 
Each  leaf  thus  received  of  a grain  (*0054  mg.)  of  the  salt; 
and  all  four  were  greatly  inflected. 

(1)  After  1 hr.  all  the  outer  tentacles  but  one  inflected,  and 
the  blade  greatly  so  ; after  7 hrs.  began  to  re-expand. 

(2)  After  1 hr.  all  the  outer  tentacles  but  eight  inflected; 
after  12  hrs.  all  re-expanded. 

(3)  After  1 hr.  much  inflection ; after  2 hrs.  30  m.  all  the  ten- 
tacles but  thirty-six  inflected ; after  6 hrs.  all  but  twenty-two 
inflected ; after  12  hrs.  partly  re-expanded. 

(4)  After  1 hr.  all  the  tentacles  but  thirty- two  inflected ; after 
2 hrs.  30  m.  all  but  twenty-one  inflected ; after  6 hrs.  almost 
re-expanded. 

Of  the  four  corresponding  leaves  in  water : — 

(1)  After  1 hr.  forty-five  tentacles  inflected ; but  after  7 hrs. 
so  many  had  re-expanded  that  only  ten  remained  much  inflected. 

(2)  After  1 hr.  seven  tentacles  inflected;  these  were  almost 
re-expanded  in  6 hrs. 

(3)  and  (4)  Not  affected,  except  that,  as  usual,  after  11  hrs. 
the  short  tentacles  on  the  borders  of  the  disc  formed  a ring. 

There  can,  therefore,  be  no  doubt  about  the  efficiency  of  the 
above  solution  ; and  it  follows  as  before  that  each  gland  of  No.  1 
could  have  absorbed  only  -g-^ilboo  ^ grain  (0000268  mg.) 
and  of  No.  2 only  yieoboo  ^ grain  (*0000263  mg.)  of  the 
phosphate. 

Seven  leaves  were  immersed,  each  in  thirty  minims  of  a 
solution  of  one  part  to  437,500  of  water  (1  gr.  to  1000  oz.). 
Each  leaf  thus  received  of  a grain  (*00405  mg.).  The  day 
was  warm,  and  the  leaves  were  very  fine,  so  that  all  circum- 
stances were  favourable. 

(1)  After  30  m.  all  the  outer  tentacles  except  five  inflected, 
and  most  of  them  closely ; after  1 hr.  blade  slightly  inflected ; 
after  9 hrs.  30  m.  began  to  re-expand. 

(2)  After  33  m.  all  the  outer  tentacles  but  twenty-five  in- 
flected, and  blade  slightly  so ; after  1 hr.  30  m.  blade  strongly 
inflected  and  remained  so  for  24  hrs. ; but  some  of  the  tentacles 
had  then  re-expanded. 

(3)  After  1 hr.  all  but  twelve  tentacles  inflected  ; after  2 hrs. 
30  m.  all  but  nine  inflected ; and  of  the  inflected  tentacles  all 
excepting  four  closely;  blade  slightly  inflected.  After  8 hrs. 
blade  quite  doubled  up,  and  now  all  the  tentacles  excepting 


162 


DROSEKA  ROTUNDIFOLIA. 


Chap.  VII. 


eight  closely  inflected.  The  leaf  remained  in  this  state  for  two 
days. 

(4)  After  2 hrs.  20  m.  only  fifty-nine  tentacles  inflected ; but 
after  5 hrs.  all  the  tentacles  closely  inflected  excepting  two 
which  were  not  affected,  and  eleven  which  were  only  sub-in- 
flected ; after  7 hrs.  blade  considerably  inflected ; after  12  hrs. 
much  re-expansion. 

(5)  After  4 hrs.  all  the  tentacles  but  fourteen  inflected ; after 
9 hrs.  30  m.  beginning  to  re-expand. 

(6)  After  1 hr.  thirty- six  tentacles  inflected;  after  5 hrs.  all 
but  fifty- four  inflected ; after  12  hrs.  considerable  re-expansion. 

(7)  After  4 hrs.  30  m.  only  thirty-five  tentacles  inflected  or 
sub-inflected,  and  this  small  amount  of  inflection  never  increased. 

Now  for  the  seven  corresponding  leaves  in  water : — 

(1)  After  4 hrs.  thirty-eight  tentacles  inflected;  but  after 
7 hrs.  these,  with  the  exception  of  six,  re-expanded. 

(2)  After  4 hrs.  20  m.  twenty  inflected;  these  after  9 hrs. 
partially  re-expanded. 

(3)  After  4 hrs.  five  inflected,  which  began  to  re-expand  after 
7 hrs. 

(4)  After  24  hrs.  one  inflected. 

(5) ,  (6)  and  (7)  Not  at  all  affected,  though  observed  for 
24  hrs.,  excepting  the  short  tentacles  on  the  borders  of  the  disc, 
which  as  usual  formed  a ring. 

A comparison  of  the  leaves  in  the  solution,  especially  of 
the  first  five  or  even  six  on  the  list,  with  those  in  the  water, 
after  1 hr.  or  after  4 hrs.,  and  in  a still  more  marked  degree 
after  7 hrs.  or  8 hrs.,  could  not  leave  the  least  doubt  that  the 
solution  had  produced  a great  effect.  This  was  shown  not  only 
by  the  vastly  greater  number  of  inflected  tentacles,  but  by 
the  degree  or  closeness  of  their  inflection,  and  by  that  of  their 
blades.  Yet  each  gland  on  leaf  No.  1 (which  bore  255  glands,  all 
of  which,  excepting  five,  were  inflected  in  30  m.)  could  not  have 
received  more  than  one-four-millionth  of  a grain  (*0000162 
mg.)  of  the  salt.  Again,  each  gland  on  leaf  No.  3 (wliich 
bore  233  glands,  all  of  which,  except  nine,  were  inflected  in 
2 hrs.  30  m.)  could  have  received  at  most  only  the 
a grain,  or  -0000181  mg. 

Four  leaves  were  immersed  as  before  in  a solution  of  one  part 
to  656,250  of  water  (1  gr.  to  1500  oz.)  ; but  on  this  occasion  I 
happened  to  select  leaves  which  were  very  little  sensitive,  as 
on  other  occasions  I chanced  to  select  unusually  sensitive 
leaves.  The  leaves  were  not  more  affected  after  12  hrs.  than 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


163 


the  four  corresponding  ones  in  water;  but  after  24  hrs.  they 
were  slightly  more  inflected.  Such  evidence,  however,  is  not  at 
all  trustworthy. 

Twelve  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  to  1,312,500  of  water  (1  gr.  to  3000  oz.);  so  that 
each  leaf  received  40^^  of  a grain  (*00135  mg,).  The  leaves  were 
not  in  very  good  condition ; four  of  them  were  too  old  and  of  a 
dark  red  colour ; four  were  too  pale,  yet  one  of  these  latter  acted 
well ; the  four  others,  as  far  as  could  be  told  by  the  eye,  seemed 
in  excellent  condition.  The  result  was  as  follows : — 

(1)  This  was  a pale  leaf ; after  40  m.  about  thirty-eight  ten- 
tacles inflected ; after  3 hrs.  30  m.  the  blade  and  many  of  the 
outer  tentacles  inflected;  after  10  hrs.  15  m.  all  the  tentacles 
but  seventeen  inflected,  and  the  blade  quite  doubled  up;  after 
24  hrs.  all  the  tentacles  but  ten  more  or  less  inflected.  Most 
of  them  were  closely  inflected,  but  twenty-five  were  only  sub- 
inflected. 

(2)  After  1 hr.  40  m.  twenty-five  tentacles  inflected;  after 
6 hrs.  all  but  twenty-one  inflected ; after  10  hrs,  all  but  sixteen 
more  or  less  inflected ; after  24  hrs.  re-expanded. 

(3)  After  1 hr.  40  m.  thirty-five  inflected;  after  6 hrs.  "a 
large  number^'  (to  quote  my  own  memorandum)  inflected, 
but  from  want  of  time  they  were  not  counted ; after  24  hrs.  re- 
expanded. 

(4)  After  1 hr.  40  m.  about  thirty  inflected  ; after  6 hrs.  “ a 
large  number  all  round  the  leaf”  inflected,  but  they  were  not 
counted ; after  10  hrs.  began  to  re-expand. 

(5)  to  (12)  These  were  not  more  inflected  than  leaves  often 
are  in  water,  having  respectively  16,  8, 10,  8,  4,  9, 14,  and  0 ten- 
tacles inflected.  Two  of  these  leaves,  however,  were  remarkable 
from  having  their  blades  slightly  inflected  after  6 hrs. 

With  respect  to  the  twelve  corresponding  leaves  in  water,  (1) 
had,  after  1 hr.  35  m.,  fifty  tentacles  inflected,  but  after  11  hrs. 
only  twenty- two  remained  so,  and  these  formed  a group,  with  the 
blade  at  this  point  slightly  inflected.  It  appeared  as  if  this  leaf 
had  been  in  some  manner  accidentally  excited,  for  instance  by  a 
particle  of  animal  matter  which  was  dissolved  by  the  water. 
(2)  After  1 hr.  45  m.  thirty-two  tentacles  inflected,  but  after 
5 hrs.  30  m.  only  twenty-five  inflected,  and  these  after  10  hrs. 
all  re-expanded;  (3)  after  1 hr.  twenty-five  inflected,  which 
after  10  hrs.  20  m.  were  all  re-expanded;  (4)  and  (5)  after 
1 hr.  35  m.  six  and  seven  tentacles  inflected,  which  re -expanded 
after  11  hrs.;  (6),  (7)  and  (8)  from  one  to  three  inflected,  which 


164 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIL 


soon  re-expanded ; (9),  (10),  (11)  and  (12)  none  inflected,  though 
observed  for  twenty-four  hours. 

Comparing  the  states  of  the  twelve  leaves  in  water  with  those 
in  the  solution,  there  could  be  no  doubt  that  in  the  latter  a larger 
number  of  tentacles  were  inflected,  and  these  to  a greater  degree ; 
but  the  evidence  was  by  no  means  so  clear  as  in  the  former  ex- 
periments with  stronger  solutions.  It  deserves  attention  that  the 
inflection  of  four  of  the  leaves  in  the  solution  went  on  increasing 
during  the  first  6 hrs.,  and  with  some  of  them  for  a longer  time ; 
whereas  in  the  water  the  inflection  of  the  three  leaves  which 
were  the  most  affected,  as  well  as  of  all  the  others,  began  to  de- 
crease during  this  same  interval.  It  is  also  remarkable  that  the 
blades  of  three  of  the  leaves  in  the  solution  were  slightly  in- 
flected, and  this  is  a most  rare  event  with  leaves  in  water, 
though  it  occurred  to  a slight  extent  in  one  (No.  1),  which 
seemed  to  have  been  in  some  manner  accidentally  excited.  All 
this  shows  that  the  solution  produced  some  effect,  though  less 
and  at  a much  slower  rate  than  in  the  previous  cases.  The 
small  effect  produced  may,  however,  be  accounted  for  in  large 
part  by  the  majority  of  the  leaves  having  been  in  a poor  con- 
dition. 

Of  the  leaves  in  the  solution.  No.  1 bore  200  glands  and  received 
Ts  000  ^ grain  of  the  salt.  Subtracting  the  seventeen  tentacles 

which  were  not  inflected,  each  gland  could  have  absorbed  only 
F784000  of  a grain  ('00000738  mg.).  This  amount  caused 
the  tentacle  bearing  each  gland  to  be  greatly  inflected.  The 
blade  was  also  inflected. 


Lastly,  eight  leaves  were  immersed,  each  in  thirty  minims  of  a 
solution  of  one  part  of  the  phosphate  to  21,875,000  of  water  (1  gr. 
to  5000  oz.).  Each  leaf  thus  received  -g oooo  of  a grain  of  the  salt, 
or  *00081  mg.  I took  especial  pains  in  selecting  the  finest  leaves 
from  the  hot-house  for  immersion,  both  in  the  solution  and  the 
water,  and  almost  all  proved  extremely  sensitive.  Beginning  as 
before  with  those  in  the  solution  : — 

(1)  After  2 hrs.  30  m.  all  the  tentacles  but  twenty-two  in- 
flected, but  some  only  sub-inflected ; the  blade  much  inflected ; 
after  6 hrs.  30  m.  all  but  thirteen  inflected,  with  the  blade 
immensely  inflected ; and  remained  so  for  48  hrs. 

(2)  No  change  for  the  first  12  hrs.,  but  after  24  hrs.  all  the 
tentacles  inflected,  excepting  those  of  the  outermost  row,  of  which 
only  eleven  were  inflected.  The  inflection  continued  to  increase, 
and  after  48  hrs.  all  the  tentacles  except  three  were  inflected. 


Chap.  VII. 


PHOSPHATE  OF  AMMONIA. 


165 


and  most  of  them  rather  closely,  four  or  five  being  only  sub- 
inflected. 

(3)  No  change  for  the  first  12  hrs. ; but  after  24  hrs.  all  the 
tentacles  excepting  those  of  the  outermost  row  were  sub-inflected, 
with  the  blade  inflected.  After  36  hrs.  blade  strongly  inflected, 
with  all  the  tentacles,  except  three,  inflected  or  sub -inflected. 
After  48  hrs.  in  the  same  state. 

(4)  to  (8)  These  leaves,  after  2 hrs.  30  m.,  had  respectively 
32,  17,  7,  4,  and  0 tentacles  inflected,  most  of  which,  after  a few 
hours,  re-expanded,  with  the  exception  of  No.  4,  which  retained 
its  thirty-two  tentacles  inflected  for  48  hrs. 

Now  for  the  eight  corresponding  leaves  in  water  : — 

(1)  After  2 hrs.  40  m.  this  had  twenty  of  its  outer  tentacles 
inflected,  five  of  which  re-expanded  after  6 hrs.  30  m.  After 
10  hrs.  15  m.  a most  unusual  circumstance  occurred,  namely, 
the  whole  blade  became  slightly  bowed  towards  the  footstalk, 
and  so  remained  for  48  hrs.  The  exterior  tentacles,  excepting 
those  of  the  three  or  four  outermost  rows,  were  now  also  in- 
flected to  an  unusual  degree. 

(2)  to  (8)  These  leaves,  after  2 hrs.  40  m.,  had  respectively  42, 
12,  9,  8,  2,  1,  and  0 tentacles  inflected,  which  all  re-expanded 
within  24  hrs.,  and  most  of  them  within  a much  shorter  time. 

When  the  two  lots  of  eight  leaves  in  the  solution  and  in  the 
water  were  compared  after  the  lapse  of  24  hrs.,  they  undoubt- 
edly differed  much  in  appearance.  The  few  tentacles  on  the 
leaves  in  water  which  were  inflected  had  after  this  interval  re- 
expanded, with  the  exception  of  one  leaf;  and  this  presented 
the  very  unusual  case  of  the  blade  being  somewhat  inflected, 
though  in  a degree  hardly  approaching  that  of  the  two  leaves  in 
the  solution.  Of  these  latter  leaves,  No.  1 had  almost  all  its 
tentacles,  together  with  its  blade,  inflected  after  an  immersion 
of  2 hrs.  30  m.  Leaves  No.  2 and  3 were  affected  at  a much 
slower  rate ; but  after  from  24  hrs.  to  48  hrs.  almost  all  their 
tentacles  were  closely  inflected,  and  the  blade  of  one  quite 
doubled  up.  We  must  therefore  admit,  incredible  as  the  fact 
may  at  first  appear,  that  this  extremely  weak  solution  acted  on 
the  more  sensitive  leaves;  each  of  which  received  only  the 
~soooo  of  ^ grain  (*00081  mg.)  of  the  phosphate.  Now,  leaf 
No.  3 bore  178  tentacles,  and  subtracting  the  three  which  were 
not  inflected,  each  gland  could  have  absorbed  only  the  TtooVooo 
of  a grain,  or  *00000463  mg.  Leaf  No.  1,  which  was  strongly 
acted  on  within  2 hrs.  30  m.,  and  had  all  its  outer  tentacles, 
except  thirteen,  inflected  within  6 hrs.  30  m.,  bore  260  tentacles ; 
and  on  the  same  principle  as  before,  each  gland  could  have 


166 


DKOSEKA  EOTUNDIFOLIA. 


Chap.  VIE 


absorbed  only  ■]  9 7 6^0000  of  a grain,  or  *00000328  mg.;  and  this 
excessively  minute  amount  sufficed  to  cause  all  the  tentacles 
bearing  these  glands  to  be  greatly  inflected.  The  blade  was  also 
inflected. 

Summary  of  the  Results  with  Phosphate  of  Ammonia, — 
The  glands  of  the  disc,  when  excited  by  a half-minim 
drop  (*0296  ml.),  containing  of  a grain  (*0169 
mg.)  of  this  salt,  transmit  a motor  impulse  to  the 
exterior  tentacles,  causing  them  to  bend  inwards.  A 
minute  drop,  containing  tttfo-o  of  a grain  (*000423 
mg.),  if  held  for  a few  seconds  in  contact  with  a 
gland,  causes  the  tentacle  bearing  this  gland  to  be 
inflected.  If  a leaf  is  left  immersed  for  a few  hours, 
and  sometimes  for  a shorter  time,  in  a solution  so 
weak  that  each  gland  can  absorb  only  the  tv)  7 Vo  0 00 
of  a grain  (*00000328  mg.),  this  is  enough  to  excite 
the  tentacle  into  movement,  so  that  it  becomes 
closely  inflected,  as  does  sometimes  the  blade.  In 
the  general  summary  to  this  chapter  a few  remarks 
will  be  added,  showing  that  the  efficiency  of  such 
extremely  minute  doses  is  not  so  incredible  as  it 
must  at  first  appear. 

Sulphate  of  Ammonia, — The  few  trials  made  with  this  and  the 
following  five  salts  of  ammonia  were  undertaken  merely  to 
ascertain  whether  they  induced  inflection.  Half-minims  of  a 
solution  of  one  part  of  the  sulphate  of  ammonia  to  437  of 
water  were  placed  on  the  discs  of  seven  leaves,  so  that  each 
received  of  a grain,  or  *0675  mg.  After  1 hr.  the  tentacles 
of  five  of  them,  as  well  as  the  blade  of  one,  were  strongly 
inflected.  1 he  leaves  were  not  afterwards  observed. 

Citrate  of  Ammonia, — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves.  In 
1 hr.  the  short  outer  tentacles  round  the  discs  were  a little 
inflected,  with  the  glands  on  the  discs  blackened.  After 
3 hrs.  25  m.  one  leaf  had  its  blade  inflected,  but  none  of  the 
exterior  tentacles.  All  six  leaves  remained  in  nearly  the  same 
state  during  the  day,  the  submarginal  tentacles,  however, 


Chap.  VII. 


OTHER  SALTS  OF  AMMONIA. 


167 


becoming  more  inflected.  After  23  brs.  three  of  the  leaves  had 
their  blades  somewhat  inflected ; and  the  submarginal  tentacles 
of  all  considerably  inflected,  but  in  none  were  the  two,  three,  or 
four  outer  rows  affected.  I have  rarely  seen  cases  like  this, 
except  from  the  action  of  a decoction  of  grass.  The  glands  on  the 
discs  of  the  above  leaves,  instead  of  being  almost  black,  as  after 
the  first  hour,  were  now  after  23  hrs.  very  pale.  I next  tried 
on  four  leaves  half-minims  of  a weaker  solution,  of  one  part  to 
1312  of  water  (1  gr.  to  3 oz.) ; so  that  each  received 
a grain  ( 0225  mg.).  After  2 hrs.  18  m.  the  glands  on  the  disc 
were  very  dark-coloured ; after  24  hrs.  two  of  the  leaves  were 
slightly  affected ; the  other  two  not  at  all. 

Acetate  of  Ammonia, — Half-minims  of  a solution  of  about  one 
part  to  109  of  water  were  placed  on  the  discs  of  two  leaves,  both 
of  which  were  acted  on  in  5 hrs.  30  m.,  and  after  23  hrs.  had 
every  single  tentacle  closely  inflected. 

Oxalate  of  Ammonia, — Half-minims  of  a solution  of  one  part 
to  218  of  water  were  placed  on  two  leaves,  which,  after  7 hrs., 
became  moderately,  and  after  23  hrs.  strongly,  inflected.  Two 
other  leaves  were  tried  with  a weaker  solution  of  one  part 
to  437  of  water ; one  was  strongly  inflected  in  7 hrs. ; the  other 
not  until  30  hrs.  had  elapsed. 

Tartrate  of  Ammonia, — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  five  leaves.  In 
31  m.  there  was  a trace  of  inflection  in  the  exterior  tentacles  of 
some  of  the  leaves,  and  this  became  more  decided  after  1 hr. 
with  all  the  leaves;  but  the  tentacles  were  never  closely  in- 
flected. After  8 hrs.  30  m.  they  began  to  re-expand.  Next 
morning,  after  23  hrs.,  all  were  fully  re-expanded,  excepting 
one  which  was  still  slightly  inflected.  The  shortness  of  the 
period  of  inflection  in  this  and  the  following  case  is  remark- 
able. 

(Jhloride  of  Ammonium,  — Half-minims  of  a solution  of  one 
part  to  437  of  water  were  placed  on  the  discs  of  six  leaves. 
A decided  degree  of  inflection  in  the  outer  and  submarginal 
tentacles  was  perceptible  in  25  m. ; and  this  increased  during 
the  next  three  or  four  hours,  but  never  became  strongly  marked. 
After  only  8 hrs.  30  m.  the  tentacles  began  to  re-expand,  and 
by  the  next  morning,  after  24  hrs.,  were  fully  re-expanded  on 
four  of  the  leaves,  but  still  slightly  inflected  on  two. 

General  Bummarij  and  Concluding  BemarJcs  on  the 
Salts  of  Ammonia. — We  have  now  seen  that  the  nine 


168 


DKOSERA  ROTUNDIFOLIA. 


Chap.  Vn. 


salts  of  ammonia  which,  were  tried,  all  cause  the  in- 
flection of  the  tentacles,  and  often  of  the  blade  of 
the  leaf.  As  far  as  can  be  ascertained  from  the 
superficial  trials  with  the  last  six  salts,  the  citrate  is 
the  least  powerful,  and  the  phosphate  certainly  by  far 
the  most.  The  tartrate  and  chloride  are  remarkable 
from  the  short  duration  of  their  action.  The  rela- 
tive efficiency  of  the  carbonate,  nitrate,  and  phos- 
phate, is  shown  in  the  following  table  by  the  smallest 
amount  which  sufiSces  to  cause  the  inflection  of  the 
tentacles. 


Solutions,  how  applied. 

1 

Carbonate  of 
Ammonia. 

i Nitrate  of 

1 Ammonia. 

Phosphate  of 
Ammonia. 

Placed  on  the  glands  of  i 
the  disc,  so  as  to  act  ( 
indirectly  on  the  outer  j 
tentacles  . . . .J 

grain,  or 
*0675  mg. 

of  a 
grain,  or 
*027  mg. 

ism  ^ 

grain,  or 
*0169  mg. 

Applied  for  a few  se-1 
conds  directly  to  the! 
gland  of  an  outer  j 
tentacle  . . . . j 

grain,  or 
*00445  mg. 

grain,  or 
• 0025  mg. 

T55SM  ^ 

grain,  or 
* 000423  mg. 

Leaf  immersed,  withl 
time  allowed  for  each  1 
gland  to  absorb  allj 
that  it  can  . . . j 

grain,  or 
•00024  mg. 

esiW  ^ 
grain,  or 
*0000937  mg. 

grain,  or 
*00000328  mg. 

Amount  absorbed  by  a. 
gland  which  suffices 
to  cause  the  aggre- 
gation of  the  proto- \ 
plasm  in  the  adjoin-] 
ing  cells  of  the  ten- 
tacles . , . . J 

grain,  or 
*00048  mg. 

From  the  experiments  tried  in  these  three  dif- 
ferent ways,  we  see  that  the  carbonate,  which  con- 
tains 23*7  per  cent,  of  nitrogen,  is  less  efficient  than 
the  nitrate,  which  contains  35  per  cent.  The  phos- 
phate contains  less  nitrogen  than  either  of  these 
salts,  namely,  only  21*2  per  cent.,  and  yet  is  far  more 


Chap.  VII. 


SUMMARY,  SALTS  OF  AMMONIA. 


169 


efficient ; its  power  no  doubt  depending  quite  as  much 
on  the  phosphorus  as  on  the  nitrogen  which  it  contains. 
We  may  infer  that  this  is  the  case,  from  the  energetic 
manner  in  which  bits  of  bone  and  phosphate  of  lime 
affect  the  leaves.  The  inflection  excited  by  the  other 
salts  of  ammonia  is  probably  due  solely  to  their  nitro- 
gen,— on  the  same  principle  that  nitrogenous  organic 
fluids  act  powerfully,  whilst  non-nitrogenous  organic 
fluids  are  powerless.  As  such  minute  doses  of  the 
salts  of  ammonia  affect  the  leaves,  we  may  feel  almost 
sure  that  Drosera  absorbs  and  profits  by  the  amount, 
though  small,  which  is  present  in  rain-water,  in  the 
same  manner  as  other  plants  absorb  these  same  salts 
by  their  roots. 

/The  smallness  of  the  doses  of  the  nitrate,  and 
more  especially  of  the  phosphate  of  ammonia,  which 
cause  the  tentacles  of  immersed  leaves  to  be  inflected, 
is  perhaps  the  most  remarkable  fact  recorded  in  this 
volume.  When  we  see  that  much  less  than  the 
millionth*  of  a grain  of  the  phosphate,  absorbed  by 
a gland  of  one  of  the  exterior  tentacles,  causes  it  to 
bend,  it  may  be  thought  that  the  effects  of  the  solu- 
tion on  the  glands  of  the  disc  have  been  overlooked ; 
namely,  the  transmission  of  a motor  impulse  from 
them  to  the  exterior  tentacles.  No  doubt  the  move- 
ments of  the  latter  are  thus  aided ; but  the  aid  thus 
rendered  must  be  insignificant;  for  we  know  that  a 
drop  containing  as  much  as  the  3-V4-0  of  a grain  placed 
on  the  disc  is  only  just  able  to  cause  the  outer  ten- 
tacles of  a highly  sensitive  leaf  to  bend.  • It  is  cer- 


* It  is  scarcely  possible  to  real-  stretch  it  along  the  wall  of  a large 
ise  what  a million  means.  The  hall;  then  mark  off  at  one  end 

best  illustration  which  I have  met  the  tenth  of  an  inch.  This  tenth 

with  is  that  given  by  Mr.  Croll,  will  represent  a hundred,  and  th« 
who  says, — Take  a narrow  strip  of  entire  strip  a million, 
paper  83  ft.  4 in.  in  length,  and 


170 


DEOSERA  ROTUNDIFOLIA. 


Chap.  Vn. 


taiuly  a most  surprising  fact  that  the  of  a 

grain,  or  in  round  numbers  the  one-twenty-millionth 
of  a grain  (*0000033  mg.),  of  the  phosphate  should 
affect  any  plant,  or  indeed  any  animal ; and  as  this 
salt  contains  35*33  per  cent,  of  water  of  crystallisation, 
the  efficient  elements  are  reduced  to  3- ^ 
grain,  or  in  round  numbers  to  one-thirty-millionth 
of  a grain  (*00000216  mg.).  The  solution,  moreover, 
in  these  experiments  was  diluted  in  the  proportion  of 
one  part  of  the  salt  to  2,187,500  of  water,  or  one  grain 
to  5000  oz.  The  reader  will  perhaps  best  realise 
this  degree  of  dilution  by  remembering  that  5000  oz. 
would  more  than  fill  a 31-gallon  cask;  and  that  to 
this  large  body  of  water  one  grain  of  the  salt  was 
added ; only  half  a drachm,  or  thirty  minims,  of  the 
solution  being  poured  over  a leaf.  Yet  this  amount 
sufficed  to  cause  the  inflection  of  almost  every  ten- 
tacle, and  often  of  the  blade  of  the  leaf. 

I am  well  aware  that  this  statement  will  at  first 
appear  incredible  to  almost  every  one.  Drosera  is  far 
from  rivalling  the  power  of  the  spectroscope,  but  it 
can  detect,  as  shown  by  the  movements  of  its  leaves,  a 
very  much  smaller  quantity  of  the  phosphate  of  am- 
monia than  the  most  skilful  chemist  can  of  any 
substance.^  My  results  were  for  a long  time  incredible 


When  my  first  observations 
were  made  on  the  nitrate  of  am- 
monia, fourteen  years  ago,  the 
powers  of  the  spectroscope  had 
not  been  discovered;  and  I felt 
all  the  greater  interest  in  the 
then  unrivalled  powers  of  Drosera. 
Now  the  spectroscope  has  al- 
together beaten  Drosera;  for  ac- 
cording to  Bunsen  and  Kirchhoff 
probably  less  than  one  of 

a grain  of  sodium  can  be  thus 
detected  (see  Balfour  Stewart, 


‘ Treatise  on  Heat,*  2nd  edit. 
1871,  p.  228).  With  respect  to 
ordinary  chemical  tests,  I gather 
from  Dr.  Alfred  Taylor’s  work 
on  ‘ Poisons  * that  about  of  a 
grain  of  arsenic,  ^ of  a grain 
of  prussic  acid,  of  iodine, 
and  of  tartarised  antimony, 
can  be  detected;  but  the  power 
of  detection  depends  much  on  the 
solutions  under  trial  not  being 
extremely  weak. 


Chap.  yil.  SUMMAKY,  SALTS  OF  AMMONIA. 


171 


even  to  myself,  and  I anxiously  sought  for  every 
source  of  error.  The  salt  was  in  some  cases  weighed 
for  me  by  a chemist  in  an  excellent  balance ; and  fresh 
water  was  measured  many  times  with  care.  The 
observations  were  repeated  during  several  years.  Two 
of  my  sons,  who  were  as  incredulous  as  myself,  compared 
several  lots  of  leaves  simultaneously  immersed  in  the 
weaker  solutions  and  in  water,  and  declared  that  there 
could  be  no  doubt  about  the  difference  in  their  ap- 
pearance. I hope  that  some  one  may  hereafter  be  in- 
duced to  repeat  my  experiments ; in  this  case  he  should 
select  young  and  vigorous  leaves,  with  the  glands 
surrounded  by  abundant  secretion.  The  leaves  should 
be  carefully  cut  off  and  laid  gently  in  watch-glasses, 
and  a measured  quantity  of  the  solution  and  of  water 
poured  over  each.  The  water  used  must  be  as  ab- 
solutely pure  as  it  can  be  made.  It  is  to  be  especially 
observed  that  the  experiments  with  the  weaker  solu- 
tions ought  to  be  tried  after  several  days  of  very 
warm  weather.  Those  with  the  weakest  solutions 
should  be  made  on  plants  which  have  been  kept 
for  a considerable  time  in  a warm  greenhouse,  or  cool 
hothouse ; but  this  is  by  no  means  necessary  for  trials 
with  solutions  of  moderate  strength. 

/ 1 beg  the  reader  to  observe  that  the  sensitiveness  or 
irritability  of  the  tentacles  was  ascertained  by  three 
different  methods — indirectly  by  drops  placed  on  the 
disc,  directly  by  drops  applied  to  the  glands  of  the 
outer  tentacles,  and  by  the  immersion  of  whole  leaves ; 
and  it  was  found  by  these  three  methods  that  the 
nitrate  was  more  p9werful  than  the  carbonate,  and  the 
phosphate  much  more  powerful  than  the  nitrate ; this 
result  being  intelligible  from  the  difference  in  the 
amount  of  nitrogen  in  the  first  two  salts,  and  from  the 
presence  of  phosphorus  in  the  third./  It  may  aid  the 


172 


DROSERA  ROTUNDIFOLIA. 


Chap.  VII. 


reader’s  faith  to  turn  to  the  experiments  with  a 
solution  of  one  grain  of  the  phosphate  to  1000  oz. 
of  water,  and  he  will  there  find  decisive  evidence  that 
the  one-four-millionth  of  a grain  is  sufficient  to  cause 
the  inflection  of  a single  tentacle.  There  is,  there- 
fore, nothing  very  improbable  in  the  fifth  of  this 
weight,  or  the  one-twenty-millionth  of  a grain,  acting 
on  the  tentacle  of  a highly  sensitive  leaf.  Again,  two 
of  the  leaves  in  the  solution  of  one  grain  to  3000 
oz.,  and  three  of  the  leaves  in  the  solution  of  one 
grain  to  5000  oz.,  were  affected,  not  only  far  more 
than  the  leaves  tried  at  the  same  time  in  water,  but 
incomparably  more  than  any  five  leaves  which  can  be 
picked  out  of  the  173  observed  by  me  at  different 
times  in  water. 

There  is  nothing  remarkable  in  the  mere  fact  of  the 
one-twenty-millionth  of  a grain  of  the  phosphate, 
dissolved  in  above  two-million  times  its  weight  of 
water,  being  absorbed  by  a gland.  All  physiologists 
admit  that  the  roots  of  plants  absorb  the  salts  of 
ammonia  brought  to  them  by  the  rain ; and  fourteen 
gallons  of  rain-water  contain*  a grain  of  ammonia, 
therefore  only  a little  more  than  twice  as  much  as  in 
the  weakest  solution  employed  by  me.  The  fact 
which  appears  truly  wonderful  is,  that  the  one-twenty- 
millionth  of  a grain  of  the  phosphate  of  ammonia 
(including  less  than  the  one-thirty-millionth  of  effi- 
cient matter),  when  absorbed  by  a gland,  should 
induce  some  change  in  it,  which  leads  to  a motor 
impulse  being  transmitted  down  the  whole  length  of 
the  tentacle,  causing  the  basal  part  to  bend,  often 
through  an  angle  of  above  180  degrees. 

Astonishing  as  is  this  result,  there  is  no  sound  reason 


Miller’s  ' Elements  of  Chemistry,’  part  ii.  p.  107,  3rd  edit.  1864. 


OuAP.  VII.  SUMMARY,  SALTS  OF  AMMONIA. 


173 


why  we  should  reject  it  as  incredible.  /Prof.  Ponders, 
of  Utrecht,  informs  me  that  from  experiments  formerly 
made  by  him  and  Dr.  De  Euyter,  he  inferred  that  less 
than  the  one-millionth  of  a grain  of  sulphate  of  atro- 
pine, in  an  extremely  diluted  state,  if  applied  directly 
to  the  iris  of  a dog,  paralyses  the  muscles  of  this  organ. 
But,  in  fact,  every  time  that  we  perceive  an  odour,  we 
have  evidence  that  infinitely  smaller  particles  act  on 
our  nerves.  When  a dog  stands  a quarter  of  a mile  to 
leeward  of  a deer  or  other  animal,  and  perceives  its 
presence,  the  odorous  particles  produce  some  change  in 
the  olfactory  nerves ; yet  these  particles  must  be  in- 
finitely smaller  * than  those  of  the  phosphate  of  am- 
monia weighing  the  one-twenty-millionth  of  a grain. 
These  nerves  then  transmit  some  influence  to  the  brain 
of  the  dog,  which  leads  to  action  on  its  part.  With  Dro- 
sera,  the  really  marvellous  fact  is,  that  a plant  without 
any  specialised  nervous  system  should  be  affected  by 
such  minute  particles;  but  we  have  no  grounds  for 
assuming  that  other  tissues  could  not  be  rendered  as 
exquisitely  susceptible  to  impressions  from  without  if 
this  were  beneficial  to  the  organism,  as  is  the  nervoms 
system  of  the  higher  animals.  ^ 


* My  son,  George  Darwin,  has 
calculated  for  me  the  diameter  of 
a sphere  of  phosphate  of  ammonia 
(specific  gravity  1*678),  weigh- 
ing the  one-twenty-millionth  of 
a grain,  and  finds  it  to  be  of 
an  inch.  Now,  Dr.  Klein  informs 
me  that  the  smallest  Micrococci, 
which  are  distinctly  discernible 
under  a power  of  800  diameters, 
are  estimated  to  be  from  * 0002  to 
*0005  of  a millimetre  — that  is, 


5'o  8 0 0 tio  T¥^-oTnr  of  an  inch 
— in  diameter.  Therefore,  an  ob- 
ject between  ^ and  of  the 
size  of  a sphere  of  the  phos- 
phate of  ammonia  of  the  above 
weight  can  be  seen  under  a high 
power ; and  no  one  supposes 
that  odorous  particles,  such  as 
those  emitted  from  the  deer  in 
the  above  illustration,  could  be 
seen  under  any  power  of  the  mi* 
croscope. 


174 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIIL 


CHAPTER  VIII. 

The  Effects  of  various  Salts  and  Acids  on  the  Leaves. 

Salts  of  sodium,  potassium,  and  other  alkaline,  earthy,  and  metallic 
salts  — Summary  on  the  action  of  these  salts  — Various  acids  — 
Summary  on  their  action. 

Having  found  that  the  salts  of  ammonia  were  so 
powerful,  I was  led  to  investigate  the  action  of  some 
other  salts.  It  will  be  convenient,  first,  to  give  a list 
of  the  substances  tried  (including  forty-nine  salts  and 
two  metallic  acids),  divided  into  two  columns,  showing 
those  which  cause  inflection,  and  those  which  do  not 
do  so,  or  only  doubtfully.  My  experiments  were  made 
by  placing  half-minim  drops  on  the  discs  of  leaves,  or, 
more  commonly,  by  immersing  them  in  the  solutions ; 
and  sometimes  by  both  methods.  A summary  of  the 
results,  with  some  concluding  remarks,  will  then  be 
given.  The  action  of  various  acids  will  afterwards  be 
described. 


Salts  causing  Inflection.  Salts  not  causing  Inflection. 

(^Arranged  in  Groups  according  to  the  Chemical  Classification  in  Watt^ 
‘ Dictionary  of  Chemistry.^) 


Sodium  carbonate,  rapid  inflec- 
tion. 

Sodium  nitrate,  rapid  inflection. 

Sodium  sulphate,  moderately 
rapid  inflection. 

Sodium  phosphate,  very  rapid  in- 
flection. 

Sodium  citrate,  rapid  inflection. 

Sodium  oxalate,  rapid  inflection. 

Sodium  chloride,  moderately  rapid 
inflection. 


Potassium  carbonate : slowly  poi* 
sonous. 

Potassium  nitrate : somewhat  poi- 
sonous. 

Potassium  sulphate. 

Potassium  phosphate. 

Potassium  citrate. 

Potassium  chloride. 


Chap.  YlII. 


EFFECTS  OF  VARIOUS  SALTS. 


175 


Salts  causing  Inflection.  Salts  not  causing  Inflection. 

(^Arranged  in  Groups  according  to  the  Chemical  Classification  in  Wall<,' 
‘ Dictionary  of  Chemistry* 


Sodium  iodide,  rather  slow  inflec- 
tion. 

Sodium  bromide,  moderately  rapid 
inflection. 

Potassium  oxalate,  slow  and 
doubtful  inflection. 

Lithium  nitrate,  moderately  rapid 
inflection. 

Caesium  chloride,  rather  slow  in- 
flection. 

Silver  nitrate,  rapid  inflection: 
quick  poison. 

Cadmium  chloride,  slow  inflection. 

Mercury  perchloride,  rapid  inflec- 
tion : quick  poison. 


Aluminium  chloride,  slow  and 
doubtful  inflection. 

Gold  chloride,  rapid  inflection : 
quick  poison. 

Tin  chloride,  slow  inflection : poi- 
sonous. 

Antimony  tartrate,  slow  inflec- 
tion : probably  poisonous. 

Arsenious  acid,  quick  inflection: 
poisonous. 

..ron  chloride,  slow  inflection : 
probably  poisonous. 

Chromic  acid,  quick  inflection : 
highly  poisonous. 

Copper  chloride,  rather  slow  in- 
flection : poisonous. 

Nickel  chloride,  rapid  inflection  : 
probably  poisonous. 

Platinum  chloride,  rapid  inflec- 
tion: poisonous. 


Potassium  iodide,  a slight,^  and 
doubtful  amount  of  inflection. 
Potassium  bromide. 


Lithium  acetate. 
Rubidium  chloride. 


Calcium  acetate. 

Calcium  nitrate. 

Magnesium  acetate. 

Magnesium  nitrate. 

Magnesium  chloride. 

Magnesium  sulphate. 

Barium  acetate. 

Barium  nitrate. 

Strontium  acetate. 

Strontium  nitrate. 

Zinc  chloride. 

Aluminium  nitrate,  a trace  of  in- 
flection. 

Aluminium  and  potassium  sul- 
phate. 

Lead  chloride. 


Manganese  chloride. 

t 

Cobalt  chloride. 


176 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIII. 


Sodium,  Carbonate  of  (pure,  given  me  by  Prof.  Hoffmann). — 
Half-minims  (*0296  ml.)  of  a solution  of  one  part  to  218  of 
water  (2  grs.  to  1 oz.)  were  placed  on  the  discs  of  twelve  leaves. 
Seven  of  these  became  well  inflected;  three  had  only  two  or 
three  of  their  outer  tentacles  inflected,  and  the  remaining  two 
were  quite  unaffected.  But  the  dose,  though  only  the  of  a 
grain  (*135  mg.),  was  evidently  too  strong,  for  three  of  the 
seven  well-inflected  leaves  were  killed.  On  the  other  hand,  one 
of  the  seven,  which  had  only  a few  tentacles  inflected,  re- 
expanded and  seemed  quite  healthy  after  48  hrs.  By  employing 
a weaker  solution  (viz.  one  part  to  437  of  water,  or  1 gr.  to 
1 oz.),  doses  of  of  a grain  (*0675  mg.)  were  given  to  six 
leaves.  Some  of  these  were  affected  in  37  m. ; and  in  8 hrs.  the 
outer  tentacles  of  all,  as  well  as  the  blades  of  two,  were  con- 
siderably inflected.  After  23  hrs.  15  m.  the  tentacles  had 
almost  re-expanded,  but  the  blades  of  the  two  were  still  just 
perceptibly  curved  inwards.  After  48  hrs.  all  six  leaves  were 
fully  re-expanded,  and  appeared  perfectly  healthy. 

Three  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  to  875  of  water  (1  gr.  to  2 oz.),  so  that  each 
received  of  a grain  (2  * 02  mg.) ; after  40  m.  the  three  were 
much  affected,  and  after  6 hrs.  45  m.  the  tentacles  of  all  and 
the  blade  of  one  closely  inflected. 

Sodium,  Nitrate  of  (pure). — Half-minims  of  a solution  of  one 
part  to  437  of  water,  containing  of  a grain  (*0675  mg.), 
were  placed  on  the  discs  of  five  leaves.  After  1 hr.  25  m.  tho 
tentacles  of  nearly  all,  and  the  blade  of  one,  were  somewhat 
inflected.  The  inflection  continued  to  increase,  and  in  21  hrs. 
15  m.  the  tentacles  and  the  blades  of  four  of  them  were  greatly 
affected,  and  the  blade  of  the  fifth  to  a slight  extent.  After  an 
additional  24  hrs.  the  four  leaves  still  remained  closely  inflected, 
whilst  the  fifth  was  beginning  to  expand.  Four  days  after  the 
solution  had  been  applied,  two  of  the  leaves  had  quite,  and  one 
had  partially,  re-expanded ; whilst  the  remaining  two  remained 
closely  inflected  and  appeared  injured. 

Three  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  to  875  of  water ; in  1 hr.  there  was  great  inflec- 
tion, and  after  8 hrs.  15  m.  every  tentacle  and  the  blades  of  all 
three  were  most  strongly  inflected. 

Sodium,  Sulphate  of. — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves.  After 
5 hrs.  30  m.  the  tentacles  of  three  of  them  (with  the  blade  of 
one)  were  considerably,  and  those  of  the  other  three  slightly, 
inflected.  After  21  hrs.  the  inflection  had  a little  decreased. 


Chap. 


SALTS  OF  SODIUM. 


177 


and  in  45  hrs.  the  leaves  were  fully  expanded,  appearing  quite 
healthy. 

Three  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  of  the  sulphate  to  875  of  water ; after  1 hr. 
30  m.  there  was  some  inflection,  which  increased  so  much  that 
in  8 hrs.  10  m.  all  the  tentacles  and  the  blades  of  all  three  leaves 
were  closely  inflected. 

Sodium,  Phosphate  of. — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves.  The 
solution  acted  with  extraordinary  rapidity,  for  in  8 m.  the  ;i'c4.ter 
tentacles  on  several  of  the  leaves  were  much  incurved.  After 
6 hrs.  the  tentacles  of  all  six  leaves,  and  the  blades  of  two,  were 
closely  inflected.  This  state  of  things  continued  for  24  hrs., 
excepting  that  the  blade  of  a third  leaf  became  incurved.  After 
48  hrs.  all  the  leaves  re-expanded.  It  is  clear  that  of  a 
grain  of  phosphate  of  soda  has  great  power  in  causing  in- 
flection. 

Sodium,  Citrate  of. — Half-minims  of  a solution  of  one  part  to 
437  of  water  were  placed  on  the  discs  of  six  leaves,  but  these 
were  not  observed  until  22  hrs.  had  elapsed.  The  sub- 
marginal tentacles  of  five  of  them,  and  the  blades  of  four,  were 
then  found  inflected ; but  the  outer  rows,  of  tentacles  were  not 
affected.  One  leaf,  which  appeared  older  than  the  others,  was 
very  little  affected  in  any  way.  After  46  hrs.  four  of  the  leaves 
were  almost  re-expanded,  including  their  blades.  Three  leaves 
were  also  immersed,  each  in  thirty  minims  of  a solution  of  one 
part  of  the  citrate  to  875  of  water;  they  were  much  acted 
on  in  25  m. ; and  after  6 hrs.  35  m.  almost  all  the  tentacles, 
including  those  of  the  outer  rows,  were  inflected,  but  not  the 
blades. 

Sodium,  Oxalate  of. — Half-minims  of  a solution  of  one  part  to 
437  of  water  were  placed  on  the  discs  of  seven  leaves;  after 
5 hrs.  30  m,  the  tentacles  of  all,  and  the  blades  of  most  of  them, 
were  much  affected.  In  22  hrs.,  besides  the  inflection  of  the 
tentacles,  the  blades  of  all  seven  leaves  were  so  much  doubled 
over  that  their  tips  and  bases  almost  touched.  On  no  other 
occasion  have  I seen  the  blades  so  strongly  affected.  Three 
leaves  were  also  immersed,  each  in  thirty  minims  of  a solution  of 
one  part  to  875  of  water ; after  30  m.  there  was  much  inflection, 
and  after  6 hrs.  35  m.  the  blades  of  two  and  the  tentacles  of  all 
were  closely  inflected. 

Sodium,  Chloride  of  (best  culinary  salt). — Half-minims  of  a 
solution  of  one  part  to  218  of  water  were  placed  on  the  discs 


178 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIH. 


of  four  leaves.  Two,  apparently,  were  not  at  all  affected  in 
48  hrs. ; the  third  had  its  tentacles  slightly  inflected;  whilst 
the  fourth  had  almost  all  its  tentacles  inflected  in  24  hrs.,  and 
these  did  not  begin  to  re-expand  until  the  fourth  day,  and  were 
not  perfectly  expanded  on  the  seventh  day.  I presume  that 
this  leaf  was  injured  by  the  salt.  Half-minims  of  a weaker 
solution,  of  one  part  to  437  of  water,  were  then  dropped  on  the 
discs  of  six  leaves,  so  that  each  received  of  a grain.  In 
1 hr^  33  m.  there  was  slight  inflection ; and  after  5 hrs.  30  m. 
the  tentacles  of  all  six  leaves  were  considerably,  but  not  closely, 
inflected.  After  23  hrs.  15  m.  all  had  completely  re-expanded, 
and  did  not  appear  in  the  least  injured. 

Three  leaves  were  immersed,  each  in  thirty  minims  of  a solu- 
tion of  one  part  to  875  of  water,  so  that  each  received  3^  of  a 
grain,  or  2*02  mg.  After  1 hr.  there  was  much  inflection; 
after  8 hrs.  30  m.  all  the  tentacles  and  the  blades  of  all  three 
were  closely  inflected.  Four  other  leaves  were  also  immersed 
in  the  solution,  each  receiving  the  same  amount  of  salt 
as  before,  viz.  of  a grain.  They  all  soon  became  inflected ; 
after  48  hrs.  they  began  to  re-expand,  and  appeared  quite  un- 
injured, though  the  solution  was  sufficiently  strong  to  taste 
saline. 

Sodium^  Iodide  of, — Half-minims  of  a solution  of  one  part  to 
437  of  water  were  placed  on  the  discs  of  six  leaves.  After 
24  hrs.  four  of  them  had  their  blades  and  many  tentacles  in- 
flected. The  other  two  had  only  their  submarginal  tentacles 
inflected ; the  outer  ones  in  most  of  the  leaves  being  but  little 
affected.  After  46  hrs.  the  leaves  had  nearly  re-expanded. 
Three  leaves  were  also  immersed,  each  in  thirty  minims  of  a 
solution  of  one  part  to  875  of  water.  After  6 hrs.  30  m.  almost 
all  the  tentacles,  and  the  blade  of  one  leaf,  were  closely  inflected. 

Sodium,  Bromide  of, — Half-minims  of  a solution  of  one  part  to 
437  of  water  were  placed  on  six  leaves.  After  7 hrs.  there  was 
some  inflection ; after  22  hrs.  three  of  the  leaves  had  their  blades 
and  most  of  their  tentacles  inflected ; the  fourth  leaf  was  very 
slightly,  and  the  fifth  and  sixth  hardly  at  all,  affected.  Three 
leaves  were  also  immersed,  each  in  thirty  minims  of  a solution 
of  one  part  to  875  of  water;  after  40  m.  there  was  some  inflec- 
tion ; after  4 hrs.  the  tentacles  of  all  three  leaves  and  the  blades 
of  two  were  inflected.  These  leaves  were  then  placed  in  water, 
and  after  17  hrs.  30  m.  two  of  them  were  almost  completely, 
and  the  third  partially,  re-expanded ; so  that  apparently  they 
were  not  injured. 


Chap.  YIIL 


SALTS  OF  POTASSIUM. 


179 


Potassium,  Carbonate  of  (pure). — Half-minims  of  a solution 
of  one  part  to  437  of  water  were  placed  on  six  leaves.  No 
effect  was  produced  in  24  hrs. ; but  after  48  hrs.  some  of  the 
leaves  had  their  tentacles,  and  one  the  blade,  considerably 
inflected.  This,  however,  seemed  the  result  of  their  being  in- 
jured ; for  on  the  third  day  after  the  solution  was  given,  three  of 
the  leaves  were  dead,  and  one  was  very  unhealthy ; the  other 
two  were  recovering,  but  with  several  of  their  tentacles  appa- 
rently injured,  and  these  remained  permanently  inflected.  It 
is  evident  that  the  of  a grain  of  this  salt  acts  as  a poison. 
Three  leaves  were  also  immersed,  each  in  thirty  minims  of  a 
solution  of  one  part  to  875  of  water,  though  only  for  9 hrs. ; and, 
very  differently  from  what  occurs  with  the  salts  of  soda,  no 
inflection  ensued. 

Potassium,  Nitrate  of, — Half-minims  of  a strong  solution,  of 
one  part  to  109  of  water  (4  grs.  to  1 oz.),  were  placed  on  the 
discs  of  four  leaves ; two  were  much  injured,  but  no  inflection 
ensued.  Eight  leaves  were  treated  in  the  same  manner,  with 
drops  of  a weaker  solution,  of  one  part  to  218  of  water.  After 
50  hrs.  there  was  no  inflection,  but  two  of  the  leaves  seemed  in- 
jured. Five  of  these  leaves  were  subsequently  tested  with  drops 
of  milk  and  a solution  of  gelatine  on  their  discs,  and  only  one 
became  inflected;  so  that  the  solution  of  the  nitrate  of  the 
above  strength,  acting  for  50  hrs.,  apparently  had  injured  or 
paralysed  the  leaves.  Six  leaves  were  then  treated  in  the  same 
manner  with  a still  weaker  solution,  of  one  part  to  437  of  water, 
and  these,  after  48  hrs.,  were  in  no  way  affected,  with  the  excep- 
tion of  perhaps  a single  leaf.  Three  leaves  were  next  immersed 
for  25  hrs.,  each  in  thirty  minims  of  a solution  of  one  part  to 
875  of  water,  and  this  produced  no  apparent  effect.  They  were 
then  put  into  a solution  of  one  part  of  carbonate  of  ammonia 
to  218  of  water ; the  glands  were  immediately  blackened,  and 
after  1 hr.  there  was  some  inflection,  and  the  protoplasmic  con- 
tents of  the  cells  became  plainly  aggregated.  This  shows  that 
the  leaves  had  not  been  much  injured  by  their  immersion  for 
25  hrs.  in  the  nitrate. 

Potassium,  Sulphate  of, — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves.  After 
20  hrs.  30  m.  no  effect  was  produced ; after  an  additional  24  hrs. 
three  remained  quite  unaffected ; two  seemed  injured,  and  the 
sixth  seemed  almost  dead  with  its  tentacles  inflected.  Never- 
theless, after  two  additional  days,  all  six  leaves  recovered.  The 
immersion  of  three  leaves  for  24  hrs.,  each  in  thirty  minims  of 


180 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIII. 


a solution  of  one  part  to  875  of  water,  produced  no  apparent 
effect.  They  were  then  treated  with  the  same  solution  of  car- 
bonate of  ammonia,  with  the  same  result  as  in  the  case  of  the 
nitrate  of  potash. 

Potassium,  Phosphate  of, — Half-minims  of  a solution  of  one 
part  to  437  of  water  were  placed  on  the  discs  of  six  leaves, 
which  were  observed  during  three  days  ; but  no  effect  was  pro- 
duced. The  partial  drying  up  of  the  fluid  on  the  disc  slightly 
drew  together  the  tentacles  on  it,  as  often  occurs  in  experi- 
ments of  this  kind.  The  leaves  on  the  third  day  appeared  quite 
healthy. 

Potassium,  Citrate  of, — Half-minims  of  a solution  of  one  part 
to  437  of  water,  left  on  the  discs  of  six  leaves  for  three  days, 
and  the  immersion  of  three  leaves  for  9 hrs.,  each  in  30  minims 
of  a solution  of  one  part  to  875  of  water,  did  not  produce  the 
least  effect. 

Potassium,  Oxalate  of, — Half-minims  were  placed  on  different 
occasions  on  the  discs  of  seventeen  leaves ; and  the  results  per- 
plexed me  much,  as  they  still  do.  Inflection  supervened  very 
slowly.  After  24  hrs.  four  leaves  out  of  the  seventeen  were  well 
inflected,  together  with  the  blades  of  two ; six  were  slightly 
affected,  and  seven  not  at  all.  Three  leaves  of  one  lot  were 
observed  for  five  days,  and  all  died;  but  in  another  lot  of 
six,  all  excepting  one  looked  healthy  after  four  days.  Three 
leaves  were  immersed  during  9 hrs.,  each  in  30  minims  of 
a solution  of  one  part  to  875  of  water,  and  were  not  in  the 
least  affected;  but  they  ought  to  have  been  observed  for  a 
longer  time. 

Potassium,  Chloride  of.  Neither  half-minims  of  a solution  of 
one  part  to  437  of  water,  left  on  the  discs  of  six  leaves  for  three 
days,  nor  the  immersion  of  three  leaves  during  25  hrs.,  in 
30  minims  of  a solution  of  one  part  to  875  of  water,  produced 
the  least  effect.  The  immersed  leaves  were  then  treated  with 
carbonate  of  ammonia,  as  described  under  nitrate  of  potash,  and 
with  the  same  result. 

Potassium,  Iodide  o/.— Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  seven  leaves.  In 
30  m.  one  leaf  had  the  blade  inflected ; after  some  hours  three 
leaves  had  most  of  their  submarginal  tentacles  mod  erately  in- 
flected; the  remaining  three  being  very  slightly  affected. 
Hardly  any  of  these  leaves  had  their  outer  tentacles  inflected. 
After  21  hrs.  all  re-expanded,  excepting  two  which  still  had  a 
few  submarginal  tentacles  inflected.  Three  leaves  were  next 


Chap.  VIH. 


EFFECTS  OF  VARIOUS  SALTS. 


181 


immersed  for  8 hrs.  40  m.,  eacli  in  30  minims  of  a solution  of 
one  part  to  875  of  water,  and  were  not  in  the  least  affected.  I 
do  not  know  what  to  conclude  from  this  conflicting  evidence ; 
but  it  is  clear  that  the  iodide  of  potassium  does  not  generally 
produce  any  marked  effect. 

Fotassium,  Bromide  of. — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves ; after 
22  hrs.  one  had  its  blade  and  many  tentacles  inflected,  but  I 
suspect  that  an  insect  might  have  alighted  on  it  and  then 
escaped;  the  five  other  leaves  were  in  no  way  affected.  I 
tested  three  of  these  leaves  with  bits  of  meat,  and  after  24  hrs. 
they  became  splendidly  inflected.  Three  leaves  were  also  im- 
mersed for  21  hrs.  in  30  minims  of  a solution  of  one  part  to  875 
of  water ; but  they  were  not  at  all  affected,  excepting  that  the 
glands  looked  rather  pale. 

Lithium,  Acetate  of. — Four  leaves  were  immersed  together  in 
a vessel  containing  120  minims  of  a solution  of  one  part  to  437 
of  water ; so  that  each  received,  if  the  leaves  absorbed  equally, 
of  a grain.  After  24  hrs.  there  was  no  inflection.  I then 
added,  for  the  sake  of  testing  the  leaves,  some  strong  solution 
(viz.  1 gr.  to  20  oz.,  or  one  part  to  8750  of  water)  of  phosphate 
of  ammonia,  and  all  four  became  in  30  m.  closely  inflected. 

Lithium,  Nitrate  of. — Four  leaves  were  immersed,  as  in  the 
last  case,  in  120  minims  of  a solution  of  one  part  to  437  of 
water ; after  1 h.  30  m.  all  four  were  a little,  and  after  24  hrs. 
greatly,  inflected.  I then  diluted  the  solution  with  some 
water,  iDut  they  still  remained  somewhat  inflected  on  the  third 
day. 

C cesium.  Chloride  of. — Four  leaves  were  immersed,  as  above,  in 
120  minims  of  a solution  of  one  part  to.  437  of  water.  After 
1 hr.  5 m.  the  glands  were  darkened ; after  4 hrs.  20  m.  there 
was  a trace  of  inflection ; after  6 hrs.  40  m.  two  leaves  were 
greatly,  but  not  closely,  and.  the  other  two  considerably  inflected. 
After  22  hrs.  the  inflection  was  extremely  great,  and  two  had 
their  blades  inflected.  I then  transferred  the  leaves  into  water, 
and  in  46  hrs.  from  their  first  immersion  they  were  almost  re- 
expanded. 

Rubidium,  Chloride  of. — Four  leaves  which  were  immersed,  as 
above,  in  120  minims  of  a solution  of  one  part  to  437  of  water, 
were  not  acted  on  in  22  hrs.  I then  added  some  of  the  strong 
solution  (1  gr.  to  20  oz.)  of  phosphate  of  ammonia,  and  in  30  m. 
all  were  immensely  inflected. 

Silver,  Nitrate  of.  — Three  leaves  were  immersed  in  ninety 


182 


DROSEKA  ROTUNDIFOLIA. 


Chap.  VIIL 


minims  of  a solution  of  one  part  to  437  of  water ; so  that  each 
received,  as  before,  ^ grain.  After  5 m.  slight  inflection, 

and  after  11  m.  very  strong  inflection,  the  glands  becoming 
excessively  black ; after  40  m.  all  the  tentacles  were  closely 
inflected.  After  6 hrs.  the  leaves  were  taken  out  of  the  solution, 
washed,  and  placed  in  water;  but  next  morning  they  were 
evidently  dead. 

Calcium,  Acetate  o/.— Four  leaves  were  immersed  in  120  minims 
of  a solution  of  one  part  to  437  of  water ; after  24  hrs.  none  of 
the  tentacles  were  inflected,  excepting  a few  where  the  blade 
joined  the  petiole;  and  this  may  have  been  caused  by  the 
absorption  of  the  salt  by  the  cut-off  end  of  the  petiole.  I then 
added  some  of  the  solution  (1  gr.  to  20  oz.)  of  phospate  of 
ammonia,  but  this  to  my  surprise  excited  only  slight  inflection, 
even  after  24  hrs.  Hence  it  would  appear  that  the  acetate  had 
rendered  the  leaves  torpid. 

Calcium,  Nitrate  of, — Four  leaves  were  immersed  in  120  minims 
of  a solution  of  one  part  to  437  of  w’ater,  but  were  not  affected 
in  24  hrs.  I then  added  some  of  the  solution  of  phosphate  of 
ammonia  (1  gr.  to  20  oz.),  but  this  caused  only  very  slight  in- 
flection after  24  hrs.  A fresh  leaf  vras  next  put  into  a mixed 
solution  of  the  above  strengths  of  the  nitrate  of  calcium  and 
phosphate  of  ammonia,  and  it  became  closely  inflected  in  between 
5 m.  and  10  m.  Half-minims  of  a solution  of  one  part  of  the 
nitrate  of  calcium  to  218  of  water  were  dropped  on  the  discs  of 
three  leaves,  but  produced  no  effect. 

Magnesium,  Acetate,  Nitrate,  and  Chloride  of, — Four  leaves  were 
immersed  in  120  minims  of  solutions,  of  one  part  to  437  of  water, 
of  each  of  these  three  salts  ; after  6 hrs.  there  was  no  inflection ; 
but  after  22  hrs.  one  of  the  leaves  in  the  acetate  was  rather  more 
inflected  than  generally  occurs  from  an  immersion  for  this 
length  of  time  in  water.  Some  of  the  solution  (1  gr.  to  20  oz.) 
of  phosphate  of  ammonia  was  then  added  to  the  three  solutions. 
The  leaves  in  the  acetate  mixed  with  the  phosphate  tmderwent 
some  inflection;  and  this  was  well  pronounced  after  24  hrs. 
Those  in  the  mixed  nitrate  were  decidedly  inflected  in  4 hrs. 
30  m.,  but  the  degree  of  inflection  did  not  afterwards  much 
increase ; whereas  the  four  leaves  in  the  mixed  chloride  were 
greatly  inflected  in  a few  minutes,  and  after  4 hrs.  had  almost 
every  tentacle  closely  inflected.  We  thus  see  that  the  acetate 
and  nitrate  of  magnesium  injure  the  leaves,  or  at  least  prevent 
the  subsequent  action  of  phosphate  of  ammonia;  whereas  the 
chloride  has  no  such  tendency. 


Chap.  VIH. 


EFFECTS  OF  VARIOUS  SALTS. 


183 


Magnesium,  Sulphate  of, — Half-minims  of  a solution  of  one  part 
to  218  of  water  were  placed  on  the  discs  of  ten  leaves,  and  pro- 
duced no  effect. 

Barium,  Acetate  of, — Four  leaves  were  immersed  in  120  minims 
of  a solution  of  one  part  to  437  of  water,  and  after  22  hrs.  there 
was  no  inflection,  but  the  glands  were  blackened.  The  leaves 
were  then  placed  in  a solution  (1  gr.  to  20  oz.)  of  phosphate  of 
ammonia,  which  caused  after  26  hrs.  only  a little  inflection  in 
two  of  the  leaves. 

Barium,  Nitrate  of, — Four  leaves  were  immersed  in  120  minims 
of  a solution  of  one  part  to  437  of  water ; and  after  22  hrs.  there 
was  no  more  than  that  slight  degree  of  inflection,  which  often 
follows  from  an  immersion  of  this  length  in  pure  water.  I 
then  added  some  of  the  same  solution  of  phosphate  of  ammonia, 
and  after  30  m.  one  leaf  was  greatly  inflected,  two  others 
moderately,  and  the  fourth  not  at  all.  The  leaves  remained 
in  this  state  for  24  hrs. 

Strontium,  Acetate  of, — Four  leaves,  immersed  in  120  minims  of 
a solution  of  one  part  to  437  of  water,  were  not  affected  in 
22  hrs.  They  were  then  placed  in  some  of  the  same  solution 
of  phosphate  of  ammonia,  and  in  25  m.  two  of  them  were 
greatly  inflected ; after  8 hrs.  the  third  leaf  was  considerably 
inflected,  and  the  fourth  exhibited  a trace  of  inflection.  They 
were  in  the  same  state  next  morning. 

Strontium,  Nitrate  of, — Five  leaves  were  immersed  in  120 
minims  of  a solution  of  one  part  to  437  of  water ; after  22  hrs. 
there  was  some  slight  inflection,  but  not  more  than  sometimes 
occurs  with  leaves  in  water.  They  were  then  placed  in  the 
same  solution  of  phosphate  of  ammonia;  after  8 hrs.  three  of 
them  were  moderately  inflected,  as  were  all  five  after  24  hrs. ; 
but  not  one  was  closely  inflected.  It  appears  that  the  nitrate  of 
strontium  renders  the  leaves  half  torpid. 

Cadmium,  Chloride  of, — Three  leaves  were  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water ; after  5 hrs. 
20  m.  slight  inflection  occurred,  which  increased  during  the 
next  three  hours.  After  24  hrs.  all  three  leaves  had  their 
tentacles  well  inflected,  and  remained  so  for  an  additional  24 
hrs. ; glands  not  discoloured. 

Mercury,  Perchloride  of, — Three  leaves  were  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water ; after  22  m. 
there  was  some  slight  inflection,  which  in  48  m.  became  well 
pronounced;  the  glands  were  now  blackened.  After  5 hrs. 
35  m.  all  the  tentacles  closely  inflected;  after  24  hrs.  still 

9 


184 


DKOSEKA  ROTUNDIFOLIA. 


Chap.  Till, 


inflected  and  discoloured.  The  leaves  were  then  removed  and 
left  for  two  days  in  water ; but  they  never  re-expanded,  being 
evidently  dead. 

Zinc,  Chloride  of. — Three  leaves  immersed  in  ninety  minims 
of  a solution  of  one  part  to  437  of  water  were  not  affected  in 
25  hrs.  30  m. 

Aluminium,  Chloride  of. — Four  leaves  were  immersed  in  120 
minims  of  a solution  of  one  part  to  437  of  water ; after  7 hrs. 
45  m.  no  inflection;  after  24  hrs.  one  leaf  rather  closely,  the 
second  moderately,  the  third  and  fourth  hardly  at  all,  inflected. 
The  evidence  is  doubtful,  but  I think  some  power  in  slowly 
causing  inflection  must  be  attributed  to  this  salt.  These  leaves 
were  then  placed  in  the  solution  (1  gr.  to  20  oz.)  of  phosphate 
of  ammonia,  and  after  7 hrs.  30  m.  the  three,  which  had  been 
but  little  affected  by  the  chloride,  became  rather  closely  in- 
flected. 

Aluminium,  Nitrate  of. — Four  leaves  were  immersed  in  120 
minims  of  a solution  of  one  part  to  437  of  water ; after  7 hrs. 
45  m.  there  was  only  a trace  of  inflection ; after  24  hrs.  one  leaf 
was  moderately  inflected.  The  evidence  is  here  again  doubtful, 
as  in  the  case  of  the  chloride  of  aluminium.  The  leaves  were 
then  transferred  to  the  same  solution,  as  before,  of  phosphate  of 
ammonia ; this  produced  hardly  any  effect  in  7 hrs.  30  m. ; but 
after  25  hrs.  one  leaf  was  pretty  closely  inflected,  the  three 
others  very  slightly,  perhaps  not  more  so  than  from  water. 

Aluminium  and  Potassium,  Sulphate  of  (common  alum). — Half- 
minims of  a solution  of  the  usual  strength  were  placed  on  the 
discs  of  nine  leaves,  but  produced  no  effect. 

Gold,  Chloride  of. — Seven  leaves  were  immersed  in  so  much  of 
a solution  of  one  part  to  437  of  water  that  each  received 
30  minims,  containing  of  a grain,  or  4*048  mg.,  of  the  chloride. 
There  was  some  inflection  in  8 m.,  which  became  extreme  in 
45  m.  In  3 hrs.  the  surrounding  fluid  was  coloured  purple,  and 
the  glands  were  blackened.  After  6 hrs.  the  leaves  were  trans- 
ferred to  water ; next  morning  they  were  found  discoloured  and 
evidently  killed.  The  secretion  decomposes  the  chloride  very 
readily;  the  glands  themselves  becoming  coated  with  the 
thinnest  layer  of  metallic  gold,  and  particles  float  about  on 
the  surface  of  the  surrounding  fluid. 

Lead,  Chloride  of.  — Three  leaves  were  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water.  After  23  hrs. 
there  was  not  a trace  of  inflection ; the  glands  were  not  blackened, 
and  the  leaves  did  not  appear  injured.  They  were  then  trans- 


Chap.  VUL 


EFFECTS  OF  VARIOUS  SALTS. 


185 


ferred  to  the  solution  (1  gr.  to  20  oz.)  of  phosphate  of  ammonia, 
and  after  24  hrs.  two  of  them  were  somewhat,  the  third  yery 
little,  inflected ; and  they  thus  remained  for  another  24  hrs. 

Tin,  Chloride  of. — ^Four  leaves  were  immersed  in  120  minims 
of  a solution  of  about  one  part  (all  not  being  dissolved)  to  437  of 
water.  After  4 hrs.  no  effect ; after  6 hrs.  30  m.  all  four  leaves 
had  their  submarginal  tentacles  inflected ; after  22  hrs.  every 
single  tentacle  and  the  blades  were  closely  inflected.  The  sur- 
rounding fluid  was  now  coloured  pink.  The  leaves  were  washed 
and  transferred  to  water,  but  next  morning  were  evidently  dead. 
This  chloride  is  a deadly  poison,  but  acts  slowly. 

Antimo7iy,  Tartrate  of. — Three  leaves  were  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water.  After  8 hrs. 
30  m.  there  was  slight  inflection;  after  24  hrs.  two  of  the  leaves 
were  closely,  and  the  third  moderately,  inflected ; glands  not 
much  darkened.  The  leaves  were  washed  and  placed  in  water, 
but  they  remained  in  the  same  state  for  48  additional  hours. 
This  salt  is  probably  poisonous,  but  acts  slowly. 

Arsenious  Acid, — A solution  of  one  part  to  437  of  water ; three 
leaves  were  immersed  in  ninety  minims ; in  25  m.  considerable 
inflection ; in  1 h.  great  inflection ; glands  not  discoloured.  After 
6 hrs.  the  leaves  were  transferred  to  water ; next  morning  they 
looked  fresh,  but  after  four  days  were  pale-coloured,  had  not 
re-expanded,  and  were  evidently  dead. 

Iron,  Chloride  of. — Three  leaves  were  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water ; in  8 hrs.  no 
inflection ; but  after  24  hrs.  considerable  inflection glands 
blackened;  fluid  coloured  yellow,  with  floating  flocculent 
particles  of  oxide  of  iron.  The  leaves  were  then  placed  in 
water ; after  48  hrs.  they  had  re-expanded  a very  little,  but  I 
think  were  killed ; glands  excessively  black. 

Chromic  Acid. — One  part  to  437  of  water ; three  leaves  were .. 
immersed  in  ninety  minims ; in  30  m.  some,  and  in  1 hr.  con- 
siderable, inflection;  after  2 hrs.  all  the  tentacles  closely  in- 
flected, with  the  glands  discoloured.  Placed  in  water,  next 
day  leaves  quite  discoloured  and  evidently  killed. 

Manganese,  Chloride  of. — Three  leaves  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water ; after  22  hrs. 
no  more  inflection  than  often  occurs  in  water;  glands  not 
blackened.  The  leaves  were  then  placed  in  the  usual  solution 
of  phosphate  of  ammonia,  but  no  inflection  was  caused  even 
after  48  hrs. 

Copper,  Chloride  of. — Three  leaves  immersed  in  ninety  minims 


186 


DROSEKA  ROTUNDIFOLIA. 


Chap.  YIII. 


of  a solution  of  one  part  to  437  of  water ; after  2 hrs.  some  inflec- 
tion ; after  3 hrs.  45  m.  tentacles  closely  inflected,  with  the 
glands  blackened.  After  22  hrs.  still  closely  inflected,  and  the 
leaves  flaccid.  Placed  in  pure  water,  next  day  evidently  dead. 
A rapid  poison. 

Nickel,  Chloride  of, — Three  leaves  immersed  in  ninety  minims 
of  a solution  of  one  part  to  437  of  water;  in  25  m.  considerable 
inflection,  and  in  3 hrs.  all  the  tentacles  clbsely  inflected.  After 
22  hrs.  still  closely  inflected;  most  of  the  glands,  but  not  all, 
blackened.  The  leaves  were  then  placed  in  water ; after  24  hrs. 
remained  inflected ; were  somewhat  discoloured,  with  the  glands 
and  tentacles  dingy  red.  Probably  killed. 

Cobalt,  Chloride  of, — Three  leaves  immersed  in  ninety  minims 
of  a solution  of  one  part  to  437  of  water ; after  23  hrs.  there 
was  not  a trace  of  inflection,  and  the  glands  were  not  more 
blackened  than  often  occurs  after  an  equally  long  immersion  in 
water. 

Platinum,  Chloride  of, — Three  leaves  immersed  in  ninety 
minims  of  a solution  of  one  part  to  437  of  water ; in  6 m.  some 
inflection,  which  became  immense  after  48  m.  After  3 hrs.  the 
glands  were  rather  pale.  After  24  hrs.  all  the  tentacles  still 
closely  inflected;  glands  colourless;  remained  in  same  state  for 
four  days;  leaves  evidently  killed. 

Concluding  JRemarks  on  the  Action  of  the  foregoing 
Salts. — Of  the  fifty-one  salts  and  metallic  acids  which 
were  tried,  twenty-five  caused  the  tentacles  to  be  in- 
flected, and  twenty-six  had  no  such  effect,  two  rather 
doubtful  cases  occurring  in  each  series.  In  the  table 
at  the  head  of  this  discussion,  the  salts  are  arranged 
according  to  their  chemical  afiinities ; but  their  action 
on  Drosera  does  not  seem  to  be  thus  governed.  The 
nature  of  the  base  is  far  more  important,  as  far  as  can 
be  judged  from  the  few  experiments  here  given,  than 
that  of  the  acid ; and  this  is  the  conclusion  at  which 
physiologists  have  arrived  with  respect  to  animals. 
We  see  this  fact  illustrated  in  all  the  nine  salts  of 
soda  causing  inflection,  and  in  not  being  poisonous 
except  when  given  in  large  doses;  whereas  seven  of 


Ghap.  Vm.  CONCLUDING  REMAKKS,  SALTS.  187 

the  corresponding  salts  of  potash  do  not  cause  inflec- 
tion, and  some  of  them  are  poisonous.  Two  of  them, 
however,  viz.  the  oxalate  and  iodide  of  potash,  slowly 
induced  a slight  and  rather  doubtful  amount  of  inflec- 
tion. This  difference  between  the  two  series  is  inter- 
esting, as  Dr.  Burden  Sanderson  informs  me  that 
sodium  salts  may  be  introduced  in  large  doses  into 
the  circulation  of  mammals  without  any  injurious 
effects ; whilst  small  doses  of  potassium  salts  cause 
death  by  suddenly  arresting  the  movements  of  the 
heart.  An  excellent  instance  of  the  different  action 
of  the  two  series  is  presented  by  the  phosphate  of 
soda  quickly  causing  vigorous  inflection,  whilst  phos- 
phate of  potash  is  quite  inefScient.  The  great  power 
of  the  former  is  probably  due  to  the  presence  of 
phosphorus,  as,  in  the  cases  of  phosphate  of  lime  and 
of  ammonia.  Z&ence  we  may  infer  that  Drosera  cannot 
obtain  phosphorus  from  the  phosphate  of  potash.  This 
is  remarkable,  as  I hear  from  Dr.  Burdon  Sanderson 
that  phosphate  of  potash  is  certainly  decomposed 
within  the  bodies  of  animals.^  Most  of  the  salts  of 
soda  act  very  rapidly ; the  iodide  acting  slowest.  The 
oxalate,  nitrate,  and  citrate  seem  to  have  a special 
tendency  to  cause  the  blade  of  the  leaf  to  be  inflected. 
The  glands  of  the  disc,  after  absorbing  the  citrate, 
transmit  hardly  any  motor  impulse  to  the  outer 
tentacles;  and  in  this  character  the  citrate  of  soda 
resembles  the  citrate  of  ammonia,  or  a decoction  of 
grass-leaves;  these  three  fluids  all  acting  chiefly  on 
the  blade. 

It  seems  opposed  to  the  rule  of  the  preponderant 
influence  of  the  base  that  the  nitrate  of  lithium 
causes  moderately  rapid  inflection,  whereas  the  acetate 
causes  none ; but  this  metal  is  closely  allied  to  sodium 


188  DKOSEEA  ROTUNDIFOLIA.  Chap.  VIII. 

and  potassium,*  which  act  so  differently ; therefore 
we  might  expect  that  its  action  would  be  inter- 
mediate. We  see,  also,  that  caesium  causes  inflection, 
and  rubidium  does  not;  and  these  two  metals  are 
allied  to  sodium  and  potassium.  Most  of  the  earthy 
salts  are  inoperative.  Two  salts  of  calcium,  four  of 
magnesium,  two  of  barium,  and  two  of  strontium,  did 
not  cause  any  inflection,  and  thus  follow  the  rule  of 
the  preponderant  power  of  the  base.  Of  three  salts 
of  aluminium,  one  did  not  act,  a second  showed  a 
trace  of  action,  and  the  third  acted  slowly  and  doubt- 
fully, so  that  their  effects  are  nearly  alike. 

Of  the  salts  and  acids  of  ordinary  metals,  seventeen 
were  tried,  and  only  four,  namely  those  of  zinc,  lead, 
manganese,  and  cobalt,  failed  to  cause  inflection.  The 
salts  of  cadmium,  tin,  antimony,  and  iron,  act  slowly ; 
and  the  three  latter  seem  more  or  less  poisonous.  The 
salts  of  silver,  mercury,  gold,  copper,  nickel,  and 
platinum,  chromic  and  arsenious  acids,  cause  great 
inflection  with  extreme  quickness,  and  are  deadly 
poisons.  It  is  surprising,  judging  from  animals,  that 
lead  and  barium  should  not  be  poisonous.  Most  of  the 
poisonous  salts  make  the  glands  black,  but  chloride  of 
platinum  made  them  very  pale.  I shall  have  occasion, 
in  the  next  chapter,  to  add  a few  remarks  on  the  dif- 
ferent effects  of  phosphate  of  ammonia  on  leaves  pre- 
viously immersed  in  various  solutions. 

Acids. 

I will  first  give,  as  in  the  case  of  the  salts,  a list 
of  the  twenty-four  acids  which  were  tried,  divided  into 
two  series,  according  as  they  cause  or  do  not  cause 


* Miller’s  ‘ Elements  of  Chemistry/  3rd  edit.  pp.  337,  448. 


Chap.  VIII. 


THE  EFFECTS  OF  ACIDS. 


189 


inflection.  After  describing  the  experiments,  a few 
concluding  remarks  will  be  added. 


Acids,  much  diluted,  which  cause 
Inflection. 

1.  Nitric,  strong  inflection;  poi- 
sonous. 

2.  Hydrochloric,  moderate  and 
slow  inflection;  not  poisonous. 

3.  Hydriodic,  strong  inflection; 
poisonous. 

4.  Iodic,  strong  inflection;  poi- 
sonous. 

5.  Sulphuric,  strong  inflection; 
somewhat  poisonous. 

6.  Phosphoric,  strong  inflection ; 
poisonous. 

7.  Boracic,  moderate  and  rather 
slow  inflection ; not  poisonous. 

8.  Formic,  very  slight  inflec- 
tion ; not  poisonous. 

9.  Acetic,  strong  and  rapid  in- 
flection ; poisonous. 

10.  Propionic,  strong  but  not  very 
rapid  inflection ; poisonous. 

11.  Oleic,  quick  inflection;  very 
poisonous. 

12.  Carbolic,  very  slow  inflection; 
poisonous. 

13.  Lactic,  slow  and  moderate  in- 
flection; poisonous. 

14.  Oxalic,  moderately  quick  in- 
flection ; very  poisonous. 

15.  l^Ialic,  very  slow  but  consider- 
able inflection;  not  poisonous. 

16.  Benzoic,  rapid  inflection;  very 
poisonous. 

17.  Succinic,  moderately  quick 
inflection ; moderately  poi- 
sonous. 

18.  Hippuric,  rather  slow  inflec- 
tion; poisonous. 

19.  Hydrocyanic,  rather  rapid  in- 
flection ; very  poisonous. 


Acids,  diluted  to  the  same 
Degree,  which  do  not  cause 
Inflection. 

1.  Gallic;  not  poisonous. 

2.  Tannic ; not  poisonous. 

3.  Tartaric ; not  poisonous. 

4.  Citric ; not  poisonous. 

5.  Uric  ; (?)  not  poisonous. 


Nit  lie  Acid —YoViX  leaves  were  placed,  each  in  thirty  minims 
of  one  part  by  weight  of  the  acid  to  437  of  water,  so  that  each 
received  of  a grain,  or  4*048  mg.  This  strength  was  chosen 
lor  this  and  most  of  the  following  experiments,  as  it  is  the  same 


190 


DKOSERA  PtOTUNDIFOLIA. 


Chap.  VIII. 


as  that  of  most  of  the  foregoing  saline  solutions.  In  2 hrs.  30  m. 
some  of  the  leaves  were  considerably,  and  in  6 hrs.  30  m.  all 
were  immensely,  inflected,  as  were  their  blades.  The  surround- 
ing fluid  was  slightly  coloured  pink,  which  always  shows  that 
the  leaves  have  been  injured.  They  were  then  left  in  water  for 
three  days;  but  they  remained  inflected  and  were  evidently 
killed.  Most  of  the  glands  had  become  colourless.  Two  leaves 
were  then  -immersed,  each  in  thirty  minims  of  one  part  to  1000 
of  water ; in  a few  hours  there  was  some  inflection ; and  after 
24  hrs.  both  leaves  had  almost  all  their  tentacles  and  blades  in- 
flected ; they  were  left  in  water  for  three  days,  and  one  partially 
re-expanded  and  recovered.  Two  leaves  were  next  immersed, 
each  in  thirty  minims  of  one  part  to  2000  of  water ; this  pro- 
duced very  little  effect,  except  that  most  of  the  tentacles  close 
to  the  summit  of  the  i)etiole  were  inflected,  as  if  the  acid  had 
been  absorbed  by  the  cut-off  end. 

Hydrochloric  Acid. — One  part  to  437  of  water;  four  leaves  were 
immersed  as  before,  each  in  thirty  minims.  After  6 hrs.  only 
one  leaf  was  considerably  inflected.  After  8 hrs.  15  m.  one  had 
its  tentacles  and  blade  well  inflected;  the  other  three  were 
moderately  inflected,  and  the  blade  of  one  slightly.  The 
surrounding  fluid  was  not  coloured  at  all  pink.  After  25  hrs. 
three  of  these  four  leaves  began  to  re-expand,  but  their  glands 
were  of  a pink  instead  of  a red  colour ; after  two  more  days 
they  fully  re -expanded ; but  the  fourth  leaf  remained  inflected, 
and  seemed  much  injured  or  killed,  with  its  glands  white. 
Four  leaves  were  then  treated,  each  with  thirty  minims  of  one  part 
to  875  of  water;  after  21  hrs.  they  were  moderately  inflected; 
and  on  being  transferred  to  water,  fully  re -expanded  in  two  days, 
and  seemed  quite  healthy. 

Hydriodic  Acid. — One  to  437  of  water;  three  leaves  were  im- 
mersed as  before,  each  in  thirty  minims.  After  45  m.  the  glands 
were  discoloured,  and  the  surrounding  fluid  became  pinkish,  but 
there  was  no  inflection.  After  5 hrs.  all  the  tentacles  were 
closely  inflected;  and  an  immense  amount  of  mucus  was  secreted, 
so  that  the  fluid  could  be  drawn  out  into  long  ropes.  The  leaves 
were  then  placed  in  water,  but  never  re-expanded,  and  were  evi- 
dently killed.  Four  leaves  were  next  immersed  in  one  part  to  875 
of  water ; the  action  was  now  slower,  but  after  22  hrs.  all  four 
leaves  were  closely  inflected,  and  were  affected  in  other  respects 
as  above  described.  These  leaves  did  not  re-expand,  though 
left  for  four  days  in  water.  This  acid  acts  far  more  powerfully 
than  hydrochloric,  and  is  poisonous. 

Iodic  Acid. — One  to  437  of  water ; three  leaves  were  immersed. 


Cbap.  VUI. 


THE  EFFECTS  OF  ACIDS. 


191 


each  in  thirty  minims ; after  3 hrs.  strong  inflection ; after  4 hrs. 
glands  dark  brown ; after  8 hrs.  30  m.  close  inflection,  and  the 
leaves  had  become  flaccid ; surrounding  fluid  not  coloured  pink. 
These  leaves  were  then  placed  in  water,  and  next  day  were 
evidently  dead. 

Sulphuric  Acid, — One  to  437  of  water;  four  leaves  were  im- 
mersed, each  in  thirty  minims;  after  4 hrs.  great  inflection; 
after  6 hrs.  surrounding  fluid  just  tinged  pink ; they  were  then 
placed  in  water,  and  after  46  hrs.  two  of  them  were  still  closely 
inflected,  two  beginning  to  re-expand  ; many  of  the  glands 
colourless.  This  acid  is  not  so  poisonous  as  hydriodic  or  iodic 
acids. 

Phosphoric  Acid, — One  to  437  of  water;  three  leaves  were 
immersed  together  in  ninety  minims;  after  5 hrs.  30  m.  some 
inflection,  and  some  glands  colourless;  after  8 hrs.  all  the 
tentacles  closely  inflected,  and  many  glands  colourless ; surround- 
ing fluid  pink.  Left  in  water  for  two  days  and  a half,  remained 
in  the  same  state  and  appeared  dead. 

Boracic  Acid, — One  to  437  of  water;  four  leaves  were  im- 
mersed together  in  120  minims ; after  6 hrs.  very  slight  inflection ; 
after  8 hrs.  15  m.  two  were  considerably  inflected,  the  other  two 
slightly.  After  24  hrs.  one  leaf  was  rather  closely  inflected, 
the  second  less  closely,  the  third  and  fourth  moderately.  The 
leaves  were  washed  and  put  into  water;  after  24  hrs.  they 
were  almost  fully  re-expanded  and  looked  healthy.  This  acid 
agrees  closely  with  hydrochloric  acid  of  the  same  strength  in 
its  power  of  causing  inflection,  and  in  not  being  poisonous. 

Fiyrmic  Acid, — Four  leaves  were  immersed  together  in  120 
minims  of  one  part  to  437  of  water ; after  40  m.  slight,  and  after 
6 hrs.  30  m.  very  moderate  inflection ; after  22  hrs.  only  a Little 
more  inflection  than  often  occurs  in  water.  Two  of  the  leaves 
were  then  washed  and  placed  in  a solution  (1  gr.  to  20  oz.)  of 
phosphate  of  ammonia;  after  24  hrs.  they  were  considerably 
inflected,  with  the  contents  of  their  cells  aggregated,  showing 
that  the  phosphate  had  acted,  though  not  to  the  full  and 
ordinary  degree. 

Acetic  Acid, — Four  leaves  were  immersed  together  in  120 
minims  of  one  part  to  437  of  water.  In  1 hr.  20  m.  the  tentacles 
of  all  four  and  the  blades  of  two  were  greatly  inflected.  After 
8 hrs.  the  leaves  had  become  flaccid,  but  still  remained  closely 
inflected,  the  surrounding  fluid  being  coloured  pink.  They  were 
then  washed  and  placed  in  water ; next  morning  they  were  still 
inflected  and  of  a very  dark  red  colour,  but  with  their  glands 
colourless.  After  another  day  they  were  dingy-coloured,  and 


192 


DROSERA  ROTUNDIFOLIA. 


Chap.  Vm. 


evidently  dead.  This  acid  is  far  more  powerful  than  formic,  and 
is  highly  poisonous.  Half-minim  drops  of  a stronger  mixture 
(viz.  one  part  by  measure  to  320  of  water)  were  placed  on  the 
discs  of  five  leaves ; none  of  the  exterior  tentacles,  only  those 
on  the  borders  of  the  disc  which  actually  absorbed  the  acid, 
became  inflected.  Probably  the  dose  was  too  strong  and  para- 
lysed the  leaves,  for  drops  of  a weaker  mixture  caused  much 
inflection ; nevertheless  the  leaves  all  died  after  two  days. 

Propionic  Acid, — Three  leaves  were  immersed  in  ninety  minims 
of  a mixture  of  one  part  to  437  of  water ; in  1 hr.  60  m.  there 
was  no  inflection ; but  after  3 hrs.  40  m.  one  leaf  was  greatly 
inflected,  and  the  other  two  slightly.  The  inflection  continued 
to  increase,  so  that  in  8 hrs.  all  three  leaves  were  closely  in- 
flected. Next  morning,  after  20  hrs.,  most  of  the  glands  were 
very  pale,  but  some  few  were  almost  black.  No  mucus  had  been 
secreted,  and  the  surrounding  fluid  was  only  just  perceptibly 
tinted  of  a pale  pink.  After  46  hrs.  the  leaves  became  slightly 
flaccid  and  were  evidently  killed,  as  was  afterwards  proved  to 
be  the  case  by  keeping  them  in  water.  The  protoplasm  in  the 
closely  inflected  tentacles  was  not  in  the  least  aggregated,  but 
towards  their  bases  it  was  collected  in  little  brownish  masses  at 
the  bottoms  of  the  cells.  This  protoplasm  was  dead,  for  on 
leaving  the  leaf  in  a solution  of  carbonate  of  ammonia,  no 
aggregation  ensued.  Propionic  acid  is  highly  poisonous  to 
Drosera,  like  its  ally  acetic  acid,  but  induces  inflection  at  a 
much  slower  rate. 

Oleic  Acid  (given  me  by  Prof.  Frankland). — Three  leaves  were 
immersed  in  this  acid ; some  inflection  was  almost  immediately 
caused,  which  increased  slightly,  but  then  ceased,  and  the  leaves 
seemed  killed.  Next  morning  they  were  rather  shrivelled,  and 
many  of  the  glands  had  fallen  off  the  tentacles.  Drops  of  this 
acid  were  placed  on  the  discs  of  four  leaves;  in  40  m.  all  the 
tentacles  were  greatly  inflected,  excepting  the  extreme  marginal 
ones ; and  many  of  these  after  3 hrs.  became  inflected.  I was 
led  to  try  this  acid  from  supposing  that  it  was  present  (which 
does  not  seem  to  be  the  case)*  in  olive  oil,  the  action  of  which 
is  anomalous.  Thus  drops  of  this  oil  placed  on  the  disc  do  not 
cause  the  outer  tentacles  to  be  inflected;  yet  when  minute 
drops  were  added  to  the  secretion  surrounding  the  glands  of  the 
outer  tentacles,  these  were  occasionally,  but  by  means  always, 
inflected.  Two  leaves  were  also  immersed  in  this  oil,  and  there 


♦ See  articles  on  Glycerine  and  Oleic  Acid  in  Watts*  ‘Diet,  of 
Chemistry.* 


Chap.  VIII. 


THE  EFFECTS  OF  ACIDS. 


193 


was  no  inflection  for  about  12  hrs.;  but  after  23  hrs.  almost  all 
the  tentacles  were  inflected.  Three  leaves  were  likewise  im- 
mersed in  unboiled  linseed  oil,  and  soon  became  somewhat,  and 
in  3 hrs.  greatly,  inflected.  After  1 hr.  the  secretion  round  the 
glands  was  coloured  pink.  I infer  from  this  latter  fact  that  the 
power  of  linseed  oil  to  cause  inflection  cannot  be  attributed  to 
the  albumin  which  it  is  said  to  contain. 

Carbolic  Acid, — Two  leaves  were  immersed  in  sixty  minims  of 
a solution  of  1 gr.  to  437  of  water ; in  7 hrs.  one  was  slightly, 
and  in  24  hrs.  both  were  closely,  inflected,  with  a surprising 
amount  of  mucus  secreted.  These  leaves  were  washed  and  left 
for  two  days  in  water ; they  remained  inflected ; most  of  their 
glands  became  pale,  and  they  seemed  dead.  This  acid  is 
poisonous,  but  does  not  act  nearly  so  rapidly  or  powerfully  as 
might  have  been  expected  from  its  known  destructive  power  on 
the  lowest  organisms.  Half-minims  of  the  same  solution  were 
placed  on  the  discs  of  three  leaves ; after  24  hrs.  no  inflection  of  the 
outer  tentacles  ensued,  and  when  bits  of  meat  were  given  them, 
they  became  fairly  well  inflected.  Again  half-minims  of  a 
stronger  solution,  of  one  part  to  218  of  water,  were  placed  on  the 
discs  of  three  leaves ; no  inflection  of  the  outer  tentacles  ensued ; 
bits  of  meat  were  then  given  as  before ; one  leaf  alone  became 
well  inflected,  the  discal  glands  of  the  other  two  appearing 
much  injured  and  dry.  We  thus  see  that  the  glands  of 
the  discs,  after  absorbing  this  acid,  rarely  transmit  any  motor 
impulse  to  the  outer  tentacles;  though  these,  when  their  own 
glands  absorb  the  acid,  are  strongly  acted  on. 

Lactic  Acid. — Three  leaves  were  immersed  in  ninety  minims  of 
one  part  to  437  of  water.  After  48  m.  there  was  no  inflection, 
but  the  surrounding  fluid  was  coloured  pink;  after  8 hrs. 
30  m.  one  leaf  alone  was  a little  inflected,  and  almost  all 
the  glands  on  all  three  leaves  were  of  a very  pale  colour. 
The  leaves  were  then  washed  and  placed  in  a solution  (1  gr. 
to  20  oz.)  of  phosphate  of  ammonia ; after  about  16  hrs.  there 
was  only  a trace  of  inflection.  They  were  left  in  the  phosphate 
for  48  hrs.,  and  remained  in  the  same  state,  with  almost  all 
their  glands  discoloured.  The  protoplasm  within  the  cells 
was  not  aggregated,  except  in  a very  few  tentacles,  the  glands 
of  which  were  not  much  discoloured.  I believe,  therefore, 
that  almost  all  the  glands  and  tentacles  had  been  killed  by 
the  acid  so  suddenly  that  hardly  any  inflection  was  caused. 
Four  leaves  were  next  immersed  in  120  minims  of  a weaker 
solution,  of  one  part  to  875  of  water;  after  2 hrs.  30  m.  the 
surrounding  fluid  was  quite  pink;  the  glands  were  pale,  but 


194 


DEOSEEA  ROTUNDIFOLIA. 


Chap.  VIII. 


there  was  no  inflection ; after  7 hrs.  30  m.  two  of  the  leaves 
showed  some  inflection,  and  the  glands  were  almost  white; 
after  21  hrs.  two  of  the  leaves  were  considerably  inflected, 
and  a third  slightly ; most  of  the  glands  were  white,  the  others 
dark  red.  After  45  hrs.  one  leaf  had  almost  every  tentacle  in- 
flected ; a second  a large  number ; the  third  and  fourth  very  few ; 
almost  all  the  glands  were  white,  excepting  those  on  the  discs  of 
two  of  the  leaves,  and  many  of  these  were  very  dark  red.  The 
leaves  appeared  dead.  Hence  lactic  acid  acts  in  a very  peculiar 
manner,  causing  inflection  at  an  extraordinarily  slow  rate,  and 
being  highly  poisonous.  Immersion  in  even  weaker  solutions, 
viz.  of  one  part  to  1312  and  1750  of  water,  apparently  killed  the 
leaves  (the  tentacles  after  a time  being  bowed  backwards),  and 
rendered  the  glands  white,  but  caused  no  inflection. 

Gallic,  Tannic,  Tartaric,  and  Citric  Acids. — One  part  to  437  of 
water.  Three  or  four  leaves  were  immersed,  each  in  thirty 
minims  of  these  four  solutions,  so  that  each  leaf  received  of  a 
grain,  or  4*048  mg.  No  inflection  was  caused  in  24  hrs.,  and  the 
leaves  did  not  appear  at  all  injured.  Those  which  had  been  in 
the  tannic  and  tartaric  acids  were  placed  in  a solution  (1  gr.  to 
20  oz.)  of  phosphate  of  ammonia,  but  no  inflection  ensued  in 
24  hrs.  On  the  other  hand,  the  four  leaves  which  had  been  in 
the  citric  acid,  when  treated  with  the  phosphate,  became  decidedly 
inflected  in  50  m.  and  strongly  inflected  after  5 hrs.,  and  so 
remained  for  the  next  24  hrs. 

Malic  Acid. — Three  leaves  were  immersed  in  ninety  minims  of 
a solution  of  one  part  to  437  of  water ; no  inflection  was  caused 
in  8 hrs.  20  m.,  but  after  24  hrs.  two  of  them  were  considerably, 
and  the  third  slightly,  inflected— more  so  than  could  be  ac- 
counted for  by  the  action  of  water.  No  great  amount  of  mucus 
was  secreted.  They  were  then  placed  in  water,  and  after  two 
days  partially  re-expanded.  Hence  this  acid  is  not  poisonous. 

Oxalic  Acid. — Three  leaves  were  immersed  in  ninety  minims  of 
a solution  of  1 gr.  to  437  of  water ; after  2 hrs.  10  m.  there  was 
much  inflection;  glands  pale;  the  surrounding  fluid  of  a dark 
pink  colour ; after  8 hrs.  excessive  inflection.  The  leaves  were 
then  placed  in  water ; after  about  16  hrs.  the  tentacles  were  of 
a very  dark  red  colour,  like  those  of  the  leaves  in  acetic  acid. 
After  24  addition al  hours,  the  three  leaves  were  dead  and  tlu'ir 
glands  colourless. 

Benzoic  Acid. — Five  leaves  were  immersed,  each  in  thirty 
minims  of  a solution  of  1 gr.  to  437  of  water.  This  solution  was 
so  weak  that  it  only  just  tasted  acid,  yet,  as  we  shall  see,  was 
highly  poisonous  to  Drosera.  After  62  m.  the  submarginal 


Chap.  VIII. 


THE  EFFECTS  OF  ACIDS. 


195 


tentacles  were  somewhat  inflected,  and  all  the  glands  yery  pale- 
coloured;  the  surrounding  fluid  was  coloured  pink.  On  one 
occasion  the-fluid  became  pink  in  the  course  of  only  12  m.,  and 
the  glands  as  white  as  if  the  leaf  had  been  dipped  in  boiling 
water.  After  4 hrs.  much  inflection ; but  none  of  the  tentacles 
were  closely  inflected,  owing,  as  I believe,  to  their  having  been 
paralysed  before  they  had  time  to  complete  their  movement. 
An  extraordinary  quantity  of  mucus  was  secreted.  Some  of  the 
leaves  were  left  in  the  solution;  others,  after  an  immersion  of 
6 hrs.  30  m.,  were  placed  in  water.  Next  morning  both  lots 
were  quite  dead;  the  leaves  in  the  solution  being  flaccid,  those 
in  the  water  (now  coloured  yellow)  of  a pale  brown  tint,  and 
their  glands  white. 

Succinic  Acid, — Three  leaves  were  immersed  in  ninety  minims 
of  a solution  of  1 gr.  to  437  of  water ; after  4 hrs.  15  m.  consider- 
able and  after  23  hrs.  great  inflection;  many  of  the  glands 
pale ; fluid  coloured  pink.  The  leaves  were  then  washed  and 
placed  in  water ; after  two  days  there  was  some  re-expansion, 
but  many  of  the  glands  were  still  white.  This  acid  is  not 
nearly  so  poisonous  as  oxalic  or  benzoic. 

Uric  Acid, — Three  leaves  were  immersed  in  180  minims  of  a 
solution  of  1 gr.  to  875  of  warm  water,  but  all  the  acid  was  not 
dissolved;  so  that  each  received  nearly  of  a grain.  After 
25  m.  there  was  some  slight  inflection,  but  this  never  increased ; 
after  9 hrs.  the  glands  were  not  discoloured,  nor  was  the  solu- 
tion coloured*  pink;  nevertheless  much  mucus  was  secreted. 
The  leaves  were  then  placed  in  water,  and  by  next  morning 
fully  re-expanded.  I doubt  whether  this  acid  really  causes 
inflection,  for  the  slight  movement  which  at  first  occurred  may 
have  been  due  to  the  presence  of  a trace  of  albuminous  matter. 
But  it  produces  some  effect,  as  shown  by  the  secretion  of  so 
much  mucus. 

Eippuric  Acid, — Four  leaves  were  immersed  in  120  minims  of 
a solution  of  1 gr.  to  437  of  water.  After  2 hrs.  the  fluid  was 
coloured  pink ; glands  pale,  but  no  inflection.  After  6 hrs.  some 
inflection;  after  9 hrs.  all  four  leaves  greatly  inflected;  much 
mucus  secreted ; all  the  glands  very  pale.  The  leaves  were  then 
left  in  water  for  two  days;  they  remained  closely  inflected, 
with  their  glands  colourless,  and  I do  not  doubt  were  killed. 

Hydrocyanic  Acid, — Four  leaves  were  immersed,  each  in  thirty 
minims  of  one  part  to  437  of  water;  in  2 hrs.  45  m.  all  the 
tentacles  were  considerably  inflected,  with  many  of  the  glands 
pale ; after  3 hrs.  45  m.  all  strongly  inflected,  and  the  surround- 
ing fluid  coloured  pink ; after  6 hrs.  all  closely  inflected.  After 


196 


DROSERA  ROTUNDIFOLIA. 


Chap.  VIIL 


an  immersion  of  8 hrs.  20  m.  the  leaves  were  washed  and  placed 
in  water;  next  morning,  after  about  16  hrs.,  they  were  still 
inflected  and  discoloured ; on  the  succeeding  day  they  were 
evidently  dead.  Two  leaves  were  immersed  in  a stronger 
mixture,  of  one  part  to  fifty  of  water ; in  1 hr.  15  m.  the  glands 
became  as  white  as  porcelain,  as  if  they  had  been  dipped  in  boil- 
ing water ; very  few  of  the  tentacles  were  inflected ; but  after 
4 hrs.  almost  all  were  inflected.  These  leaves  were  then  placed 
in  water,  and  next  morning  were  evidently  dead.  Half-minim 
drops  of  the  same  strength  (viz.  one  part  to  fifty  of  water)  were 
next  placed  on  the  discs  of  five  leaves ; after  21  hrs.  all  the 
outer  tentacles  were  inflected,  and  the  leaves  appeared  much 
injured.  I likewise  touched  the  secretion  round  a large  number 
of  glands  with  minute  drops  (about  of  a minim,  or  *00296  ml.) 
of  Scheele’s  mixture  (6  per  cent.) ; the  glands  first  became  bright 
red,  and  after  3 hrs.  15  m.  about  two-thirds  of  the  tentacles 
bearing  these  glands  were  inflected,  and  remained  so  for  the  two 
succeeding  days,  when  they  appeared  dead. 

Concluding  BemarJcs  on  the  Action  of  Acids, — It  is 
evident  that  acids  have  a strong  tendency  to  cause  the 
inflection  of  the  tentacles ; ^ for  out  of  the  twenty-four 
acids  fried,  nineteen  thus  acted,  either  rapidly  and 
energetically,  or  slowly  and  slightly.  This  fact  is 
remarkable,  as  the  juices  of  many  plants  contain  more 
acid,  judging  by  the  taste,  than  the  solutions  employed 
in  my  experiments.  From  the  powerful  effects  of  so 
many  acids  on  Drosera,  we  are  led  to  infer  that  those 
naturally  contained  in  the  tissues  of  this  plant,  as  well 
as  of  others,  must  play  some  important  part  in  their 
economy.  Of  the  flve  cases  in  which  acids  did  not 
cause  the  tentacles  to  be  inflected,  one  is  doubtful; 
for  uric  acid  did  act  slightly,  and  caused  a copious 
secretion  of  mucus.  Mere  sourness  to  the  taste  is  no 


* According  to  M.  Fournier  Berberis  instantly  to  close;  though 
He  la  Fecondation  dans  les  drops  of  water  have  no  such  power, 
Phanerogames.^  1863,  p.  61)  drops  which  latter  statement  I can  con* 
of  acetic,  hydrocyanic,  and  sul-  firm, 
phuric  acid  ca^jpe  the  stamens  of 


Chap.  VIII.  CONCLUDING  REMARKS,  ACIDS. 


197 


eriterion  of  the  power  of  an  acid  on  Drosera,  as  citric 
and  tartaric  acids  are  very  sour,  yet  do  not  excite 
inflection.  It  is  remarkable  how  acids  differ  in 
their  power.  / Thus,  hydrochloric  acid  acts  far  less 
powerfully  than  hydriodic  and  many  other  acids  of  the 
same  strength,  and  is  not  poisonous.'  This  is  an  in- 
teresting fact,  as  hydrochloric  acid  plays  so  important 
a part  in  the  digestive  process  of  animals.  Formic 
acid  induces  very  slight  inflection,  and  is  not  poison- 
ous; whereas  its  ally,  acetic  acid,  acts  rapidly  and 
powerfully,  and  is  poisonous.  Malic  acid  acts  slightly, 
whereas  citric  and  tartaric  acids  produce  no  effect. 
Lactic  acid  is  poisonous,  and  is  remarkable  from  in- 
ducing inflection  only  after  a considerable  interval  of 
time.  Nothing  surprised  me  more  than  that  a solution 
of  benzoic  acid,  so  weak  as  to  be  hardly  acidulous  to 
the  taste,  should  act  with  great  rapidity  and  be  highly 
poisonous;  for  I am  informed  that  it  produces  no 
marked  effect  on  the  animal  economy.  It  may  be 
seen,  by  looking  down  the  list  at  the  head  of  this  dis- 
cussion, that  most  of  the  acids  are  poisonous,  often 
highly  so.  Diluted  acids  are  known  to  induce  nega- 
tive osmose,*  and  the  poisonous  action  of  so  many 
acids  on  Drosera  is,  perhaps,  connected  with  this 
power,  for  we  have  seen  that  the  fluids  in  which  they 
were  immersed  often  became  pink,  and  the  glands 
pale-coloured  or  white.  Many  of  the  poisonous  acids, 
such  as  hydriodic,  benzoic,  hippuric,  and  carbolic  (but 
I neglected  to  record  all  the  cases),  caused  the  secre- 
tion of  an  extraordinary  amount  of  mucus,  so  that 
long  ropes  of  this  matter  hung  from  the  leaves  when 
they  were  lifted  out  of  the  solutions.  Other  acids, 
such  as  hydrochloric  and  malic,  have  no  such  ten- 


* Miller’s  ‘ Elements  of  Chemistry,’  part  i.  1867,  p.  87. 


198 


DEOSERA  ROTUNDIFOLIA. 


Chap.  VIII. 


dency  ; in  these  two  latter  cases  the  surrounding  fluid 
was  not  coloured  pink,  and  the  leaves  were  not 
poisoned.  On  the  other  hand,  propionic  acid,  which 
is  poisonous,  does  not  cause  much  mucus  to  be 
secreted,  yet  the  surrounding  fluid  became  slightly 
pink.  Lastly,  as  in  the  case  of  saline  solutions, 
leaves,  after  being  immersed  in  certain  acids,  were 
soon  acted  on  by  phosphate  of  ammonia ; on  the 
other  hand,  they  were  not  thus  affected  after  immer- 
sion in  certain  other  acids.  To  this  subject,  how- 
‘^ver,  I shall  have  to  recur. 


Chap.  IX. 


ALKALOID  POISONS. 


199 


CHAPTEE  IX. 

The  Effects  of  certain  Alkaloid  Poisons,  other  Substai;ces  and 
Vapours. 

Strychnine,  salts  of — Quinine,  sulphate  of,  does  not  soon  arrest  the 
movement  of  the  protoplasm  — Other  salts  of  quinine  — Digitaline 

— N icotine  — Atropine  — ^ V eratrine — Colchicine — Theine — Curare 

— Morphia  — Hyoscyamus  — Poison  of  the  cobra,  apparently  acce- 
lerates the  movements  of  the  protoplasm  — Camphor,  a powerful 
stimulant,  its  vapour  narcotic  — Certain  essential  oils  excite  move- 
ment— Glycerine  — Water  and  certain  solutions  retard  or  prevent 
the  subsequent  action  of  phosphate  of  ammonia  — Alcohol  inno- 
cuous, its  vapour  narcotic  and  poisonous  — Chloroform,  sulphuric 
and  nitric  ether,  their  stimulant,  poisonous,  and  narcotic  power  — 
Carbonic  acid  narcotic,  not  quickly  poisonous — Concluding  remarks. 

As  in  the  last  chapter,  I will  first  give  my  experiments, 
and  then  a brief  summary  of  the  results  with  some 
concluding  remarks. 

Acetate  of  Strychnine, — Half-minims  of  a solution  of  one  part  to 
437  of  water  were  placed  on  the  discs  of  six  leaves;  so  that 
each  received  of  a grain,  or  .0675  mg.  In  2 hrs.  30  m.  the 
outer  tentacles  on  some  of  them  were  inflected,  but  in  an  irregu- 
lar manner,  sometimes  only  on  one  side  of  the  leaf.  The  next 
morning,  after  22  hrs.  30  m.,  the  inflection  had  not  increased. 
The  glands  on  the  central  disc  were  blackened,  and  had  ceased 
secreting.  After  an  additional  24  hrs.  all  the  central  glands 
seemed  dead,  but  the  inflected  tentacles  had  re-expanded  and 
appeared  quite  healthy.  Hence  the  poisonous  action  of  strych- 
nine seems  confined  to  the  glands  which  have  absorbed  it ; 
nevertheless,  these  glands  transmit  a motor  impulse  to  the 
exterior  tentacles.  Minute  drops  (about  gV  ^f  ^ minim)  of 
the  same  solution  applied  to  the  glands  of  the  outer  tentacles 
occasionally  caused  them  to  bend.  The  poison  does  not  seem 
to  act  quickly,  for  having  applied  to  several  glands  similar 
drops  of  a rather  stronger  solution,  of  one  part  to  292  of  water, 
this  did  not  prevent  the  tentacles  bending,  when  their  glands 


200 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


were  excited,  after  an  interval  of  a quarter  to  three  quarters  of 
an  hour,  by  being  rubbed  or  given  bits  of  meat.  Similar  drops 
of  a solution  of  one  part  to  218  of  water  (2  grs.  to  1 oz.)  quickly 
blackened  the  glands ; some  few  tentacles  thus  treated  moved, 
whilst  others  did  not.  The  latter,  however,  on  being  subse- 
quently moistened  with  saliva  or  given  bits  of  meat,  became 
incurved,  though  with  extreme  slowness;  and  this  shows  that 
they  had  been  injured.  Stronger  solutions  (but  the  strength 
was  not  ascertained)  sometimes  arrested  all  power  of  movement 
very  quickly ; thus  bits  of  meat  were  placed  on  the  glands  of 
several  exterior  tentacles,  and  as  soon  as  they  began  to  move, 
minute  drops  of  the  strong  solution  were  added.  They  con- 
tinued for  a short  time  to  go  on  bending,  and  then  suddenly 
stood  still;  other  tentacles  on  the  same  leaves,  with  meat 
on  their  glands,  but  not  wetted  with  the  strychnine,  continued 
to  bend  and  soon  reached  the  centre  of  the  leaf. 

Citrate  of  Strychnine, — Half-minims  of  a solution  of  one  part 
to  437  of  water  were  placed  on  the  discs  of  six  leaves;  after 
24  hrs.  the  outer  tentacles  showed  only  a trace  of  inflection. 
Bits  of  meat  were  then  placed  on  three  of  these  leaves,  but  in 
24  hrs.  only  slight  and  irregular  inflection  occurred,  proving 
that  the  leaves  had  been  greatly  injured.  Two  of  the  leaves  to 
which  meat  had  not  been  given  had  their  discal  glands  dry  and 
much  injured.  Minute  drops  of  a strong  solution  of  one  part  to 
109  of  water  (4  grs.  to  1 oz.)  were  added  to  the  secretion  round 
several  glands,  but  did  not  produce  nearly  so  plain  an  effect  as 
the  drops  of  a much  weaker  solution  of  the  acetate.  Particles  of 
the  dry  citrate  were  placed  on  six  glands ; two  of  these  moved 
some  way  towards  the  centre,  and  then  stood  still,  being  no 
doubt  killed ; three  others  curved  much  farther  inwards,  and 
were  then  fixed;  one  alone  reached  the  centre.  Five  leaves 
were  immersed,  each  in  thirty  minims  of  a solution  of  one  part 
to  437  of  water;  so  that  each  received  of  a grain;  after 
about  1 hr.  some  of  the  outer  tentacles  became  inflected,  and 
the  glands  were  oddly  mottled  with  black  and  white.  These 
glands,  in  from  4 hrs.  to  5 hrs.,  became  whitish  and  opaque, 
and  the  protoplasm  in  the  cells  of  the  tentacles  was  well  aggre- 
gated. By  this  time  two  of  the  leaves  were  greatly  inflected, 
but  the  three  others  not  much  more  inflected  than  they  were 
before.  Nevertheless  two  fresh  leaves,  after  an  immersion  re- 
spectively for  2 hrs.  and  4 hrs.  in  the  solution,  were  not  killed ; 
for  on  being  left  for  1 hr.  30  m.  in  a solution  of  one  part  of 
carbonate  of  ammonia  to  218  of  water,  their  tentacles  became 
more  inflected,  and  there  was  much  aggregation.  The  glands 


Chap.  IX. 


ALKALOID  POISONS. 


201 


of  two  other  leaves,  after  an  immersion  for  2 hrs.  in  a stronger 
solution,  of  one  part  of  the  citrate  to  218  of  water,  became  of  an 
opaque,  pale  pink  colour,  which  before  long  disappeared,  leaving 
them  white.  One  of  these  two  leaves  had  its  blade  and 
tentacles  greatly  inflected;  the  other  hardly  at  all;  but  the 
protoplasm  in  the  cells  of  both  was  aggregated  down  to  the 
bases  of  the  tentacles,  with  the  spherical  masses  in  the  cells 
close  beneath  the  glands  blackened.  After  21  hrs.  one  of  these 
leaves  was  colourless,  and  evidently  dead. 

Sulphate  of  Quinine. — Some  of  this  salt  was  added  to 
water,  which  is  said  to  dissolve  of  if®  weight. 

Five  leaves  were  immersed,  each  in  thirty  minims  of  this  solu- 
tion, which  tasted  bitter.  In  less  than  1 hr.  some  of  them  had 
a few  tentacles  inflected.  In  3 hrs.  most  of  the  glands  became 
whitish,  others  dark-coloured,  and  many  oddly  mottled.  After 
6 hrs.  two  of  the  leaves  had  a good  many  tentacles  inflected,  but 
this  very  moderate  degree  of  inflection  never  increased.  One  of 
the  leaves  was  taken  out  of  the  solution  after  4 hrs.,  and  placed 
in  water;  by  the  next  morning  some  few  of  the  inflected 
tentacles  had  re-expanded,  showing  that  they  were  not  dead; 
but  the  glands  were  still  much  discoloured.  Another  leaf  not 
included  in  the  above  lot,  after  an  immersion  of  3 hrs.  15  m., 
was  carefully  examined;  the  protoplasm  in  the  cells  of  the 
outer  tentacles,  and  of  the  short  green  ones  on  the  disc,  had 
become  strongly  aggregated  down  to  their  bases ; and  I distinctly 
saw  that  the  little  masses  changed  their  positions  and  shapes 
rather  rapidly ; some  coalescing  and  again  separating.  I was 
surprised  at  this  fact,  because  quinine  is  said  to  arrest  all  move- 
ment in  the  white  corpuscles  of  the  blood ; but  as,  according  to 
Binz,*  this  is  due  to  their  being  no  longer  supplied  with  oxygen 
by  the  red  corpuscles,  any  such  arrestment  of  movement  could 
not  be  expected  in  Drosera.  That  the  glands  had  absorbed  some 
of  the  salt  was  evident  from  their  change  of  colour ; but  I at 
first  thought  that  the  solution  might  not  have  travelled  down 
the  cells  of  the  tentacles,  where  the  protoplasm  was  seen  in 
active  movement.  This  view,  however,  I have  no  doubt,  is 
erroneous,  for  a leaf  which  had  been  immersed  for  3 hrs.  in  the 
quinine  solution  was  then  placed  in  a little  solution  of  one  part  of 
carbonate  of  ammonia  to  218  of  water ; and  in  30  m.  the  glands 
and  the  upper  cells  of  the  tentacles  became  intensely  black,  with 
the  protoplasm  presenting  a very  unusual  appearance;  for  it 


* ‘ Quarterly  Journal  of  Microscopical  Science,’  April  1874,  p.  185. 


202 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


had  become  aggregated  into  reticulated  dingy-colonred  masses, 
having  rounded  and  angular  interspaces.  As  I have  never 
seen  this  effect  produced  by  the  carbonate  of  ammonia  alone, 
it  must  be  attributed  to  the  previous  action  of  the  quinine. 
These  reticulated  masses  were  watched  for  some  time,  but  did 
not  change  their  forms ; so  that  the  protoplasm  no  doubt  had 
been  killed  by  the  combined  action  of  the  two  salts,  though 
exposed  to  them  for  only  a short  time. 

Another  leaf,  after  an  immersion  for  24  hrs.  in  the  quinine 
solution,  became  somewhat  flaccid,  and  the  protoplasm  in  all 
the  cells  was  aggregated.  Many  of  the  aggregated  masses  were 
discoloured,  and  presented  a granular  appearance ; they  were 
spherical,  or  elongated,  or  still  more  commonly  consisted  of 
little  curved  chains  of  small  globules.  None  of  these  masses 
exhibited  the  least  movement,  and  no  doubt  were  all  dead. 

Half-minims  of  the  solution  were  placed  on  the  discs  of  six 
leaves;  after  23  hrs.  one  had  all  its  tentacles,  two  had  a few, 
and  the  others  none  inflected ; so  that  the  discal  glands,  when 
irritated  by  this  salt,  do  not  transmit  any  strong  motor  impulse 
to  the  outer  tentacles.  After  48  hrs.  the  glands  on  the  discs  of 
all  six  leaves  were  evidently  much  injured  or  quite  killed.  It  is 
clear  that  this  salt  is  highly  poisonous.* 

Acetate  of  Quinine, — Four  leaves  were  immersed,  each  in  thirty 
minims  of  a solution  of  one  part  to  437  of  water.  The  solution 
was  tested  with  litmus  paper,  and  was  not  acid.  After  only 
10  m.  all  four  leaves  were  greatly,  and  after  6 hrs.  immensely, 
inflected.  They  were  then  left  in  water  for  60  hrs.,  but  never 
re-expanded ; the  glands  were  white,  and  the  leaves  evidently 
dead.  This  salt  is  far  more  efficient  than  the  sulphate  in 
causing  inflection,  and,  like  that  salt,  is  highly  poisonous. 

Nitrate  of  Quinine, — Four  leaves  were  immersed,  each  in  thirty 
minims  of  a solution  of  one  part  to  437  of  water.  After  6 hrs. 
there  was  hardly  a trace  of  inflection ; after  22  hrs.  three  of  the 
leaves  were  moderately,  and  the  fourth  slightly  inflected;  so 
that  this  salt  induces,  though  rather  slowly,  well-marked  inflec- 
tion. These  leaves,  on  being  left  in  water  for  48  hrs.,  almost 


* Binz  found  several  years  ago 
(as  stated  in  ‘The  Journal  of 
Anatomy  and  Phys.’  November 
1872,  p.  195)  that  quinia  is  an 
energetic  poison  to  low  vege- 
table and  animal  organisms.  Even 
one  part  added  to  4000  parts  of 
])lood  arrests  the  movements  of  the 


white  corpuscles,  which  become 
“ rounded  and  granular.’*  In  the 
tentacles  of  Drosera  the  aggre- 
gated masses  of  protoplasm,  which 
appeared  killed  by  the  quinine, 
likewise  presented  a granular 
appearance.  A similar  appear- 
ance is  caused  by  very  hot  water 


Chap.  IX. 


ALKALOID  POISONS. 


203 


completely  re-expanded,  but  the  glands  were  mnch  discoloured. 
Hence  this  salt  is  not  poisonous  in  any  high  degree.  The 
different  action  of  the  three  foregoing  salts  of  quinine  is  sin- 
gular. 

Digitaline. — Half-miiiims  of  a solution  of  one  part  to  437  of 
water  were  placed  on  the  discs  of  five  leaves.  In  3 hrs.  45  m. 
some  of  them  had  their  tentacles,  and  one  had  its  blade, 
moderately  inflected.  After  8 hrs.  three  of  them  were  well  in- 
flected; the  fourth  had  only  a few  tentacles  inflected,  and  the 
fifth  (an  old  leaf T was  not  at  all  affected.  They  remained  in 
nearly  the  same  state  for  two  days,  but  the  glands  on  their  discs 
became  pale.  On  the  third  day  the  leaves  appeared  much 
injured.  Nevertheless,  when  bits  of  meat  were  placed  on  two 
of  them,  the  outer  tentacles  became  inflected.  A minute  drop 
(about  of  a minim)  of  the  solution  was  applied  to  three 
glands,  and  after  6 hrs.  all  three  tentacles  were  inflected,  but 
next  day  had  nearly  re-expanded ; so  that  this  very  small  dose 
of  of  a grain  (*00225  mg.)  acts  on  a tentacle,  but  is  not 
poisonous.  It  appears  from  these  several  facts  that  digitaline 
causes  inflection,  and  poisons  the  glands  which  absorb  a 
moderately  large  amount. 

Nicotine. — The  secretion  round  several  glands  was  touched 
with  a minute  drop  of  the  pure  fluid,  and  the  glands  were 
instantly  blackened;  the  tentacles  becoming  inflected  in  a few 
minutes.  Two  leaves  were  immersed  in  a weak  solution  of  two 
drops  to  1 oz.,  or  437  grains,  of  water.  When  examined 
after  3 hrs.  20  m.,  only  twenty-one  tentacles  on  one  leaf  were 
closely  inflected,  and  six  on  the  other  slightly  so ; but  all  the 
glands  were  blackened,  or  very  dark-coloured,  with  the  pro- 
toplasm in  all  the  cells  of  all  the  tentacles  much  aggregated 
and  dark-coloured.  The  leaves  were  not  quite  killed,  for  on 
being  placed  in  a little  solution  of  carbonate  of  ammonia 
(2  grs.  to  1 oz.)  a few  more  tentacles  became  inflected,  the 
remainder  not  being  acted  on  during  the  next  24  hrs. 

Half-minims  of  a stronger  solution  (two  drops  to  5 oz.  of 
water)  were  placed  on  the  discs  of  six  leaves,  and  in  30  m.  all 
those  tentacles  became  inflected ; the  glands  of  which  had 
actually  touched  the  solution,  as  shown  by  their  blackness  ; 
but  hardly  any  motor  influence  was  transmitted  to  the  outer 
tentacles.  After  22  hrs.  most  of  the  glands  on  the  discs  ap- 
peared dead ; but  this  could  not  have  been  the  case,  as  when 
bits  of  meat  were  placed  on  three  of  them,  some  few  of  the 
outer  tentacles  were  inflected  in  24  hrs.  Hence  nicotine  has  a 
great  tendency  to  blacken  the  glands  and  to  induce  aggregation 


204 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX 


of  tlie  protoplasm,  but,  except  when  pure,  has  very  moderate 
power  of  inducing  inflection,  and  still  less  power  of  causing 
a motor  influence  to  be  transmitted  from  the  discal  glands  to 
the  outer  tentacles.  It  is  moderately  poisonous. 

Atropine.— A.  grain  was  added  to  437  grains  of  water,  but 
was  not  all  dissolved ; another  grain  was  added  to  437  grains  of 
a mixture  of  one  part  of  alcohol  to  seven  parts  of  water;  and 
a third  solution  was  made  by  adding  one  part  of  valerianate  of 
atropine  to  437  of  water.  Half-minims  of  these  three  solutions 
were  placed,  in  each  case,  on  the  discs  of  six  leaves;  but  no 
effect  whatever  was  produced,  excepting  that  the  glands  on 
the  discs  to  which  the  valerianate  was  given  were  slightly 
discoloured.  The  six  leaves  on  which  drops  of  the  solution 
of  atropine  in  diluted  alcohol  had  been  left  for  21  hrs. 
were  given  bits  of  meat,  and  all  became  in  24  hrs.  fairly  well 
inflected;  so  that  atropine  does  not  excite  movement,  and  is 
not  poisonous.  I also  tried  in  the  same  manner  the  alkaloid 
sold  as  daturine,  which  is  believed  not  to  differ  from  atropine, 
and  it  produced  no  effect.  Three  of  the  leaves  on  which  drops 
of  this  latter  solution  had  been  left  for  24  hrs.  were  likewise 
given  bits  of  meat,  and  they  had  in  the  course  of  24  hrs.  a good 
many  of  their  submarginal  tentacles  inflected. 

Veratrine^  Colchicine,  Theine. — Solutions  were  made  of  these 
three  alkaloids  by  adding  one  part  to  437  of  water.  Half-minims 
were  placed,  in  each  case,  on  the  discs  of  at  least  six  leaves,  but 
no  inflection  was  caused,  except  perhaps  a very  slight  amount 
by  the  theine.  Half-minims  of  a strong  infusion  of  tea  like- 
wise produced,  as  formerly  stated,  no  effect.  I also  tried  similar 
drojDS  of  an  infusion  of  one  part  of  the  extract  of  colchicum,  sold 
by  druggists,  to  218  of  water ; and  the  leaves  were  observed  for 
48  hrs.,  without  any  effect  being  produced.  The  seven  leaves  on 
which  drops  of  veratrine  had  been  left  for  26  hrs.  were  given 
bits  of  meat,  and  after  21  hrs.  were  well  inflected.  These  three 
alkaloids  are  therefore  quite  innocuous. 

Curare. — One  part  of  this  famous  poison  was  added  to  218  of 
water,  and  three  leaves  were  immersed  in  ninety  minims  of  the 
filtered  solution.  In  3 hrs.  30  m.  some  of  the  tentacles  were 
a little  inflected ; as  was  the  blade  of  one,  after  4 hrs.  After 
7 hrs.  the  glands  were  wonderfully  blackened,  showing  that 
matter  of  some  kind  had  been  absorbed.  In  9 hrs.  two  of  the 
leaves  had  most  of  their  tentacles  sub-inflected,  but  the  inflec- 
tion did  not  increase  in  the  course  of  24  hrs.  One  of  these 
leaves,  after  being  immersed  for  9 hrs.  in  the  solution,  was 
placed  in  water,  and  by  next  morning  had  largely  re-expanded ; 


Chap.  IX. 


ALKALOID  POISONS. 


205 


the  other  two,  after  their  immersion  for  24  hrs.,  were  likewise 
placed  in  water,  and  in  24  hrs.  were  considerably  re-expanded, 
though  their  glands  were  as  black  as  ever.  Half-minims  were 
placed  on  the  discs  of  six  leaves,  and  no  inflection  ensued ; but 
after  three  days  the  glands  on  the  discs  appeared  rather  dry, 
yet  to  my  surprise  were  not  blackened.  On  another  occasion 
drops  were  placed  on  the  discs  of  six  leaves,  and  a considerable 
amount  of  inflection  was  soon  caused ; but  as  I had  not  filtered 
the  solution,  floating  particles  may  have  acted  on  the  glands. 
After  24  hrs.  bits  of  meat  were  placed  on  the  discs  of  three  of 
these  leaves,  and  next  day  they  became  strongly  inflected.  As  I 
at  first  thought  that  the  poison  might  not  have  been  dissolved 
in  pure  water,  one  grain  was  added  to  437  grains  of  a mixture 
of  one  part  of  alcohol  to  seven  of  water,  and  half-minims  were 
placed  on  the  discs  of  six  leaves.  These  were  not  at  all  affected, 
and  when  after  a day  bits  of  meat  were  given  them,  they  were 
slightly  inflected  in  5 hrs.,  and  closely  after  24  hrs.  It  follows 
from  these  several  facts  that  a solution  of  curare  induces  a very 
moderate  degree  of  inflection,  and  this  may  perhaps  be  due  to 
the  presence  of  a minute  quantity  of  albumen.  It  certainly  is 
not  poisonous.  The  protoplasm  in  one  of  the  leaves,  which  had 
been  immersed  for  24  hrs.,  and  which  had  become  slightly  in- 
flected, had  undergone  a very  slight  amount  of  aggregation — 
not  more  than  often  ensues  from  an  immersion  of  this  length  of 
time  in  water. 

Acetate  of  Morphia, — I tried  a great  number  of  experiments 
with  this  substance,  but  with  no  certain  result.  A considerable 
number  of  leaves  were  immersed  from  between  2 hrs.  and  6 hrs. 
in  a solution  of  one  part  to  218  of  water,  and  did  not  become 
inflected.  Nor  were  they  poisoned ; for  when  they  were  washed 
and  placed  in  weak  solutions  of  phosphate  and  carbonate  of 
ammonia,  they  soon  became  strongly  inflected,  with  the  pro- 
toplasm in  the  cells  well  aggregated.  If,  however,  whilst  the 
leaves  were  immersed  in  the  morphia,  phosphate  of  am- 
monia was  added,  inflection  did  not  rapidly  ensue.  Minute 
drops  of  the  solution  were  applied  in  the  usual  manner  to  the 
secretion  round  between  thirty  and  forty  glands;  and  when, 
after  an  interval  of  6 m.,  bits  of  meat,  a little  saliva,  or  particles 
of  glass,  were  placed  on  them,  the  movement  of  the  tentacles 
was  greatly  retarded.  But  on  other  occasions  no  such  retar- 
dation occurred.  Drops  of  water  similarly  applied  never  have 
any  retarding  power.  Minute  drops  of  a solution  of  sugar  of 
the  same  strength  (one  part  to  218  of  water)  sometimes  retarded 
the  subsequent  action  of  meat  and  of  particles  of  glass,  and 


206 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX 


sometimes  did  not  do  so.  At  one  time  I felt  convinced  that 
morphia  acted  as  a narcotic  on  Drosera,  but  after  having  found 
in  what  a singular  manner  immersion  in  certain  non-poisonous 
salts  and  acids  prevents  the  subsequent  action  of  phosphate  of 
ammonia,  whereas  other  solutions  have  no  such  power,  my 
first  conviction  seems  very  doubtful. 

Extract  of  Hyoscyamus, — Several  leaves  were  placed,  each  in 
thirty  minims  of  an  infusion  of  3 grs.  of  the  extract  sold  by 
druggists  to  1 oz.  of  water.  One  of  them,  after  being  immersed 
for  5 hrs.  15  m.,  was  not  inflected,  and  was  then  put  into  a 
solution  (1  gr.  to  1 oz.)  of  carbonate  of  ammonia ; after  2 hrs. 
40  m.  it  was  found  considerably  inflected,  and  the  glands 
much  blackened.  Four  of  the  leaves,  after  being  immersed  for 
2 hrs.  14  m.,  were  placed  in  120  minims  of  a solution  (1  gr.  to 
20  oz.)  of  phosphate  of  ammonia;  they  had  already  become 
slightly  inflected  from  the  hyoscyamus,  probably  owing  to  the 
presence  of  some  albuminous  matter,  as  formerly  explained, 
but  the  inflection  immediately  increased,  and  after  1 hr.  was 
strongly  pronounced ; so  that  hyoscyamus  does  not  act  as  a 
narcotic  or  poison. 

Poison  from  the  Fang  of  a Living  Adder, — Minute  drops  were 
placed  on  the  glands  of  many  tentacles;  these  were  quickly 
inflected,  just  as  if  saliva  had  l^en  given  them.  Next  morning, 
after  17  hrs.  30  m.,  all  were  beginning  to  re-expand,  and  they 
appeared  uninjured. 

Poison  from  the  Cobra. — Dr.  Fayrer,  well  known  from  his 
investigations  on  the  poison  of  this  deadly  snake,  was  so  kind 
as  to  give  me  some  in  a dried  state.  It  is  an  albuminous 
substance,  and  is  believed  to  replace  the  ptyaline  of  saliva.  * A 
minute  drop  (about  ^ of  a minim)  of  a solution  of  one  part  to 
437  of  water  was  applied  to  the  secretion  round  four  glands ; so 
that  each  received  only  about  ssloo  ^ grain  (*0016  mg.).  Tho 
operation  was  repeated  on  four  other  glands;  and  in  15  m. 
several  of  the  eight  tentacles  became  well  inflected,  and  all  of 
them  in  2 hrs.  Next  morning,  after  24  hrs.,  they  were  still 
inflected,  and  the  glands  of  a very  pale  pink  colour.  After  an 
additional  24  hrs.  they  were  nearly  re-expanded,  and  completely 
so  on  the  succeeding  day;  but  most  of  the  glands  remained 
almost  white. 

Half-minims  of  the  same  solution  were  placed  on  the  discs  of 
three  leaves,  so  that  each  received  g of  a grain  (*0675  mg.) ; in 


Dr.  Fayrer,  ‘ The  Thanatophidia  of  India,*  1872,  p.  150 


Chap.  IX. 


POISOX  OF  THE  COBRA. 


207 


4 lirs.  15  m.  the  outer  tentacles  were  much  inflected ; and  after 
6 hrs.  30  m.  those  on  two  of  the  leaves  were  closely  inflected  and 
the  blade  of  one ; the  third  leaf  was  only  moderately  affected. 
The  leaves  remained  in  the  same  state  during  the  next  day, 
but  after  48  hrs.  re-expanded. 

Three  leaves  were  now  immersed,  each  in  thirty  minims  of  the 
solution,  so  that  each  received  yV  of  a grain,  or  4*048  mg.  In 
6 m.  there  was  some  inflection,  which  steadily  increased,  so  that 
after  2 hrs.  30  m.  all  three  leaves  were  closely  inflected ; the 
glands  were  at  first  somewhat  darkened,  then  rendered  pale ; and 
the  protoplasm  within  the  cells  of  the  tentacles  was  partially 
aggregated.  The  little  masses  of  protoplasm  were  examined 
after  3 hrs.,  and  again  after  7 hrs.,  and  on  no  other  occasion 
have  I seen  them  undergoing  such  rapid  changes  of  form. 
After  8 hrs.  30  m.  the  glands  had  become  quite  white ; they  had 
not  secreted  any  great  quantity  of  mucus.  The  leaves  were 
now  placed  in  water,  and  after  40  hrs.  re-expanded,  showing  that 
they  were  not  much  or  at  all  injured.  During  their  immersion 
in  water  the  protoplasm  within  the  cells  of  the  tentacles  was 
occasionally  examined,  and  always  found  in  strong  movement. 

Two  leaves  were  next  immersed,  each  in  thirty  minims  of  a 
much  stronger  solution,  of  one  part  to  109  of  water ; so  that  each 
received  ^ of  a grain,  or  16*2  mg.  After  1 hr.  45  m.  the  sub- 
marginal tentacles  were  strongly  inflected,  with  the  glands  some- 
what pale ; after  3 hrs.  30  m.  both  leaves  had  all  their  tentacles 
closely  inflected  and  the  glands  white.  Hence  the  weaker 
solution,  as  in  so  many  other  cases,  induced  more  rapid  inflec- 
tion than  the  stronger  one ; but  the  glands  were  sooner  rendered 
white  by  the  latter.  After  an  immersion  of  24  hrs.  some  of  the 
tentacles  were  examined,  and  the  protoplasm,  still  of  a fine 
purple  colour,  was  found  aggregated  into  chains  of  small  globular 
masses.  These  changed  their  shapes  with  remarkable  quickness. 
After  an  immersion  of  48  hrs.  they  were  again  examined,  and 
their  movements  were  so  plain  that  they  could  easily  be  seen 
under  a weak  power.  The  leaves  were  now  placed  in  water, 
and  after  24  hrs.  (i.e.  72  hrs.  from  their  first  immersion)  the 
little  masses  of  protoplasm,  which  had  become  of  a dingy  purple, 
were  still  in  strong  movement,  changing  their  shapes,  coalescing, 
and  again  separating. 

In  8 hrs.  after  these  two  leaves  had  been  placed  in  water  (i.e. 
in  56  hrs.  after  their  immersion  in  the  solution)  they  began  to 
re-expand,  and  by  the  next  morning  were  more  expanded. 
After  an  additional  day  (i.e.  on  the  fourth  day  after  their  immer- 
sion in  the  solution)  they  were  largely,  but  not  quite  fully 
10 


208 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


expanded.  The  tentacles  were  now  examined,  and  the  aggregated 
masses  were  almost  wholly  redissolved ; the  cells  being  filled  with 
homogeneous  purple  fluid,  with  the  exception  here  and  there  of 
a single  globular  mass.  We  thus  see  how  completely  the  proto- 
plasm had  escaped  all  injury  from  the  poison.  As  the  glands 
were  soon  rendered  quite  white,  it  occurred  to  me  that  their 
texture  might  have  been  modified  in  such  a manner  as  to 
prevent  the  poison  passing  into  the  cells  beneath,  and  conse- 
quently that  the  protoplasni  within  these  cells  had  not  been  at 
all  affected.  Accordingly  I placed  another  leaf,  which  had  been 
immersed  for  48  hrs.  in  the  poison  and  afterwards  for  24  hrs.  in 
water,  in  a little  solution  of  one  part  of  carbonate  of  ammonia 
to  218  of  water ; in  30  m.  the  protoplasm  in  the  cells  beneath 
the  glands  became  darker,  and  in  the  course  of  24  hrs.  the 
tentacles  were  filled  down  to  their  bases  with  dark-coloured 
spherical  masses.  Hence  the  glands  had  not  lost  their 
power  of  absorption,  as  far  as  the  carbonate  of  ammonia  is 
concerned. 

From  these  facts  it  is  manifest  that  the  poison  of  the  cobra, 
though  so  deadly  to  animals,  is  not  at  all  poisonous  to  Drosera ; 
yet  it  causes  strong  and  rapid  inflection  of  the  tentacles,  and 
soon  discharges  all  colour  from  the  glands.  It  seems  even  to  act 
as  a stimulant  to  the  protoplasm,  for  after  considerable  expe- 
rience in  observing  the  movements  of  this  substance  in  Drosera, 
I have  never  seen  it  on  any  other  occasion  in  so  active  a state.  I 
was  therefore  anxious  to  learn  how  this  poison  affected  animal 
protoplasm ; and  Dr.  Fayrer  was  so  kind  as  to  make  some  obser- 
vations for  me,  which  he  has  since  published.*  Ciliated  epi- 
thelium from  the  mouth  of  a frog  was  placed  in  a solution  of 
*03  gramme  to  4’6  cubic  cm.  of  water  ; others  being  placed 
at  the  same  time  in  pure  water  for  comparison.  The  move- 
ments of  the  cilia  in  the  solution  seemed  at  first  increased, 
but  soon  languished,  and  after  between  15  and  * 20  minutes 
ceased ; whilst  those  in  the  water  were  still  acting  vigorously. 
The  white  corpuscles  of  the  blood  of  a frog,  and  the  cilia  on  two 
infusorial  animals,  a Paramsecium  and  Volvox,  were  similarly 
affected  by  the  poison.  Dr.  Fayrer  also  found  that  the  muscle 
of  a frog  lost  its  irritability  after  an  immersion  of  20  m.  in 
the  solution,  not  then  responding  to  a strong  electrical  current. 
On  the  other  hand,  the  movements  of  the  cilia  on  the  mantle  of 
an  Unio  were  not  always  arrested,  even  when  left  for  a consider- 


* ‘ Proceedings  of  Royal  Society,*  Feb.  18,  1875. 


Chap.  IX. 


CAMPHOR. 


209 


able  time  in  a very  strong  solution.  On  the  whole,  it  seems 
that  the  poison  of  the  cobra  acts  far  more  injuriously  on  the 
protoplasm  of  the  higher  animals  than  on  that  of  Drosera. 

There  is  one  other  point  which  may  be  noticed.  I have  occa- 
sionally observed  that  the  drops  of  secretion  round  the  glands 
were  rendered  somewhat  turbid  by  certain  solutions,  and  more 
especially  by  some  acids,  a film  being  formed  on  the  surfaces  of 
the  drops;  but  I never  saw  this  effect  produced  in  so  con- 
spicuous a manner  as  by  the  cobra  poison.  When  the  stronger 
solution  was  employed,  the  drops  appeared  in  10  m.  like  little 
white  rounded  clouds.  After  48  hrs.  the  secretion  was  changed 
into  threads  and  sheets  of  a membranous  substance,  including 
minute  granules  of  various  sizes. 

Camphor, — Some  scraped  camphor  was  left  for  a day  in  a bottle 
with  distilled  water,  and  then  filtered.  A solution  thus  made  is 
said  to  contain  -5^^^  of  its  weight  of  camphor;  it  smelt  and 
tasted  of  this  substance.  Ten  leaves  were  immersed  in  this 
solution;  after  15  m.  five  of  them  were  well  inflected,  two 
showing  a first  trace  of  movement  in  11  m.  and  12  m. ; the 
sixth  leaf  did  not  begin  to  move  until  15  m.  had  elapsed,  but 
was  fairly  well  inflected  in  17  m.  and  quite  closed  in  24  m. ; the 
seventh  began  to  move  in  17  m.,  and  was  completely  shut  in 
26  m.  The  eighth,  ninth,  and  tenth  leaves  were  old  and  of 
a very  dark  red  colour,  and  these  were  not  inflected  after  an 
immersion  of  24  hrs.;  so  that  in  making  experiments  with 
camphor  it  is  necessary  to  avoid  such  leaves.  Some  of  these 
leaves,  on  being  left  in  the  solution  for  4 hrs.,  became  of  a 
rather  dingy  pink  colour,  and  secreted  much  mucus ; although 
their  tentacles  were  closely  inflected,  the  protoplasm  within  the 
cells  was  not  at  all  aggregated.  On  another  occasion,  however, 
after  a longer  immersion  of  24  hrs.,  there  was  well  marked 
aggregation.  A solution  made  by  adding  two  drops  of  campho- 
rated spirits  to  an  ounce  of  water  did  not  act  on  one  leaf; 
whereas  thirty  minims  added  to  an  ounce  of  water  acted  on  two 
leaves  immersed  together. 

M.  Vogel  has  shown*  that  the  flowers  of  various  plants  do  not 
wither  so  soon  when  their  stems  are  placed  in  a solution  of  cam- 
phor as  when  in  water;  and  that  if  already  slightly  withered, 
they  recover  more  quickly.  The  germination  of  certain  seeds  is 
also  accelerated  by  the  solution.  So  that  camphor  acts  as  a 
stimulant,  and  it  is  the  only  known  stimulant  for  plants.  I 


* ‘ Gardener’s  Chronicle,’  1874,  p.  671.  Nearly  similar  observationt 
were  made  in  1798  by  B.  S.  Barton. 


210 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


wished,  therefore,  to  ascertain  whether  camphor  would  render  the 
leaves  of  Drosera  more  sensitive  to  mechanical  irritation  than 
they  naturally  are.  Six  leaves  were  left  in  distilled  water  for 
5 m.  or  6 m.,  and  then  gently  brushed  twice  or  thrice,  whilst  still 
under  water,  with  a soft  camel-hair  brush ; but  no  movement 
ensued.  Nine  leaves,  which  had  been  immersed  in  the  above 
solution  of  camphor  for  the  times  stated  in  the  following 
table,  were  next  brushed  only  once  with  the  same  brush  and  in 
the  same  manner  as  before ; the  results  are  given  in  the  table. 
My  first  trials  were  made  by  brushing  the  leaves  whilst  still 
immersed  in  the  solution ; but  it  occurred  to  me  that  the  viscid 
secretion  round  the  glands  would  thus  be  removed,  and  the 
camphor  might  act  more  effectually  on  them.  In  all  the 
following  trials,  therefore,  each  leaf  was  taken  out  of  the  solu- 
tion, waved  for  about  15  s.  in  water,  then  placed  in  fresh  water 
and  brushed,  so  that  the  brushing  would  not  allow  the  freer 
access  of  the  camphor ; but  this  treatment  made  no  difference 
in  the  results. 


Number  of  Leaves, 

i 

Length  of  | 
Immersion  in ' 
the  Solution 
of  Camphor. 

Length  of  Time  between  the  Act  of  Brushing 
and  the  Inflection  of  the  Tentacles. 

Length  of 
Time  between 
the  Immersion 
of  the  Leaves  in 
the  Solution 
and  the  First 
Sign  of  the 
Inflection  of  the 

1 Tentacles. 

1 

5 m. 

J3  m.  considerable  inflection  ; 4 m.  alll 
\ the  tentacles  except  3 or  4 inflected.  / 

8 m. 

2 

5 m. 

6 m.  first  sign  of  inflection. 

11  m. 

3 

5 m. 

|6  m,  30  s.  slight  inflection ; 7 m.  30  s.\ 
\ plain  inflection.  j 

11  m.  30  s. 

4 

4 m.  30  s. 

(2  m.  30  s.  a trace  of  inflection ; 3 m.l 
\ plain ; 4 m.  strongly  marked.  / 

7 m. 

5 

4 m. 

|2  m.  30  s.  a trace  of  inflection;  3 m.\ 
\ plain  inflection.  / 

6 m.  30  s. 

6 

4 m. 

r 2 m.  30  s.  decided  inflection ; 3 m.  30  s.\ 
\ strongly  marked.  / 

6 m.  30  s. 

7 

4 m. 

J2  m.  30  s.  slight  inflection;  3 m.I 
\ plain ; 4 m.  well  marked.  f 

G m.  30  s. 

8 

3 m. 

(2  m.  trace  of  inflection  ; 3 m.  con-1 
\ siderable,  6 m.  strong  inflection.  / 

0 m. 

3 m. 

(2  m.  trace  of  inflection ; 3 m.  con-  i 

0 m. 

9 

t siderable,  6 rn.  strong  inflection,  f 

Other  leaves  were  left  in  the  solution  without  being  brushed ; 
one  of  these  first  showed  a trace  of  inflection  after  11  m.;  a 
second  after  12  m.;  five  were  not  inflected  until  15  m.  had 


Chap.  IX. 


ESSENTIAL  OILS,  ETC. 


211 


elapsed,  and  two  not  until  a few  minutes  later.  On  the  other 
hand,  it  will  be  seen  in  the  right-hand  column  of  the  table  that 
most  of  the  leaves  subjected  to  the  solution,  and  which  were 
brushed,  became  inflected  in  a much  shorter  time.  The  move- 
ment of  the  tentacles  of  some  of  these  leaves  was  so  rapid  that 
it  could  be  plainly  seen  through  a very  weak  lens. 

Two  or  three  other  experiments  are  worth  giving.  A large 
old  leaf,  after  being  immersed  for  10  m.  in  the  solution,  did  not 
appear  likely  to  be  soon  inflected ; so  I brushed  it,  and  in  2 m. 
it  began  to  move,  and  in  3 m.  was  completely  shut.  Another 
leaf,  after  an  immersion  of  15  m.,  showed  no  signs  of  inflection, 
so  was  brushed,  and  in  4 m.  was  grandly  inflected.  A third  leaf, 
after  an  immersion  of  17  m.,  likewise  showed  no  signs  of  in- 
flection; it  was  then  brushed,  but  did  not  move  for  1 hr.;  so 
that  here  was  a failure.  It  was  again  brushed,  and  now  in 
9 m.  a few  tentacles  became  inflected ; the  failure  therefore  was 
not  complete. 

We  may  conclude  that  a small  dose  of  camphor  in  solution  is  a 
powerful  stimulant  to  Drosera.  It  not  only  soon  excites  the  ten- 
tacles to  bend,  but  apparently  renders  the  glands  sensitive  to  a 
touch,  which  by  itself  does  not  cause  any  movement.  Or  it  may 
be  that  a slight  mechanical  irritation  not  enough  to  cause  any 
inflection  yet  gives  some  tendency  to  movement,  and  thus 
reinforces  the  action  of  the  camphor.  This  latter  view  would 
have  appeared  to  me  the  more  probable  one,  had  it  not  been 
shown  by  M.  Vogel  that  camphor  is  a stimulant  in  other  ways  to 
various  plants  and  seeds. 

Two  plants  bearing  four  or  five  leaves,  and  with  their  roots 
in  a little  cup  of  water,  were  exposed  to  the  vapour  of  some 
bits  of  camphor  (about  as  large  as  a filbert-nut),  under  a 
vessel  holding  ten  fluid  ounces.  After  10  hrs.  no  inflection 
ensued ; but  the  glands  appeared  to  be  secreting  more  copiously. 
The  leaves  were  in  a narcotised  condition,  for  on  bits  of  meat 
being  placed  on  two  of  them,  there  was  no  inflection  in  3 hrs. 
15  m.,  and  even  after  13  hrs.  15  m.  only  a few  of  the  outer 
tentacles  were  slightly  inflected;  but  this  degree  of  movement 
shows  that  the  leaves  had  not  been  killed  by  an  exposure 
during  10  hrs.  to  the  vapour  of  camphor. 

Oil  of  Caraway. — Water  is  said  to  dissolve  about  a thousandth 
part  of  its  weight  of  this  oil.  A drop  was  added  to  an  ounce 
of  water  and  the  bottle  occasionally  shaken  during  a day; 
but  many  minute  globules  remained  undissolved.  Five  leaves 
were  immersed  in  this  mixture ; in  from  4 m.  to  5 m.  there  was 
Borne  inflection,  which  became  moderately  pronounced  in  two  or 


212 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


three  additional  minutes.  After  14  m.  all  five  leaves  were  well, 
and  some  of  them  closely,  inflected.  After  6 hrs.  the  glands  were 
white,  and  much  mucus  had  been  secreted.  The  leaves  were 
now  flaccid,  of  a peculiar  dull-red  colour,  and  evidently  dead. 
One  of  the  leaves,  after  an  immersion  of  4 m.,  was  brushed,  like  the 
leaves  in  the  camphor,  but  this  produced  no  effect.  A plant 
with  its  roots  in  water  was  exposed  under  a 10-oz.  vessel  to  the 
vapour  of  this  oil,  and  in  1 hr.  20  m.  one  leaf  showed  a trace  of 
inflection.  After  5 hrs.  20  m.  the  cover  was  taken  off  and  the 
leaves  examined;  one  had  all  its  tentacles  closely  inflected, 
the  second  about  half  in  the  same  state ; and  the  third  all  sub- 
inflected. The  plant  was  left  in  the  open  air  for  42  hrs.,  but  not 
a single  tentacle  expanded ; all  the  glands  appeared  dead,  except 
here  and  there  one,  which  was  still  secreting.  It  is  evident 
that  this  oil  is  highly  exciting  and  poisonous  to  Drosera. 

Oil  of  Cloves, — A mixture  was  made  in  the  same  manner  as  in 
the  last  case,  and  three  leaves  were  immersed  in  it.  After  30  m. 
there  was  only  a trace  of  inflection  which  never  increased.  After 
1 hr.  30  m.  the  glands  were  pale,  and  after  6 hrs.  white.  No 
doubt  the  leaves  were  much  injured  or  killed. 

Turpentine, — Small  drops  placed  on  the  discs  of  some  leaves 
killed  them,  as  did  likewise  drops  of  creosote.  A plant  was  left 
for  15  m.  under  a 12-oz.  vessel,  with  its  inner  surface  wetted 
with  twelve  drops  of  turpentine ; but  no  movement  of  the  ten- 
tacles ensued.  After  24  hrs.  the  plant  was  dead. 

Glycerine, — Half-minims  were  placed  on  the  discs  of  three 
leaves : in  2 hrs.  some  of  the  outer  tentacles  were  irregularly 
inflected ; and  in  19  hrs.  the  leaves  were  flaccid  and  apparently 
dead ; the  glands  which  had  touched  the  glycerine  were  colour- 
less. Minute  drops  (about  gV  ^ minim)  were  applied  to  the 
glands  of  several  tentacles,  and  in  a few  minutes  these  moved 
and  soon  reached  the  centre.  Similar  drops  of  a mixture 
of  four  dropped  drops  to  1 oz.  of  water  were  likewise  applied 
to  several  glands ; but  only  a few  of  the  tentacles  moved,  and 
these  very  slowly  and  slightly.  Half-minims  of  this  same  mix- 
ture placed  on  the  discs  of  some  leaves  caused,  to  my  surprise,  no 
inflection  in  the  course  of  48  hrs.  Bits  of  meat  were  then  given 
them,  and  next  day  they  were  well  inflected ; notwithstanding 
that  some  of  the  discal  glands  had  been  rendered  almost  colour- 
less. Two  leaves  were  immersed  in  the  same  mixture,  but  only 
for  4 hrs.;  they  were  not  inflected,  and  on  being  afterwards 
left  for  2 hrs.  30  m.  in  a solution  (1  gr.  to  1 oz.)  of  carbonate  of 
ammonia,  their  glands  were  blackened,  their  tentacles  inflected, 
and  the  protoplasm  within  their  cells  aggregated.  It  appears 


Chap.  IX.  EFFECTS  OF  PEEVIOUS  IMMERSION. 


213 


from  these  facts  that  a mixture  of  four  drops  of  glycerine  to 
an  ounce  of  water  is  not  poisonous,  and  excites  very  little  in- 
flection; but  that  pure  glycerine  is  poisonous,  and  if  applied 
in  very  minute  quantities  to  the  glands  of  the  outer  tentacles 
causes  their  inflection. 

The  Effects  of  Immersion  in  Water  and  in  various  Solutioiis  on 
the  subsequent  Action  of  Phosphate  and  Carbonate  of  Ammonia. — 
We  have  seen  in  the  third  and  seventh  chapters  that  immersion 
in  distilled  water  causes  after  a time  some  degree  of  aggregation 
of  the  protoplasm,  and  a moderate  amount  of  inflection,  espe- 
cially in  the  case  of  plants  which  have  been  kept  at  a rather 
high  temperature.  Water  does  not  excite  a copious  secretion 
of  mucus.  We  have  here  to  consider  the  effects  of  immersion 
in  various  fluids  on  the  subsequent  action  of  salts  of  ammonia 
and  other  stimulants.  Four  leaves  which  had  been  left  for 
24  hrs.  in  water  were  given  bits  of  meat,  but  did  not  clasp  them. 
Ten  leaves,  after  a similar  immersion,  were  left  for  24  hrs.  in 
a powerful  solution  (1  gr.  to  20  oz.)  of  phosphate  of  ammonia, 
and  only  one  showed  even  a trace  of  inflection.  Three  of 
these  leaves,  on  being  left  for  an  additional  day  in  the  solution, 
still  remained  quite  unaffected.  When,  however,  some  of  these 
leaves,  which  had  been  first  immersed  in  water  for  24  hrs.,  and 
then  in  the  phosphate  for  24  hrs.  were  placed  in  a solution  of 
carbonate  of  ammonia  (one  part  to  218  of  water),  the  pro- 
toplasm in  the  cells  of  the  tentacles  became  in  a few  hours 
strongly  aggregated,  showing  that  this  salt  had  been  absorbed 
and  taken  effect. 

A short  immersion  in  water  for  20  m.  did  not  retard  the  sub- 
sequent action  of  the  phosphate,  or  of  splinters  of  glass  placed 
on  the  glands ; but  in  two  instances  an  immersion  for  50  m.  pre- 
vented any  effect  from  a solution  of  camphor.  Several  leaves 
which  had  been  left  for  20  m.  in  a solution  of  one  part  of  white 
sugar  to  218  of  water  were  placed  in  the  phosphate  solution, 
the  action  of  which  was  delayed ; whereas  a mixed  solution  of 
sugar  and  the  phosphate  did  not  in  the  least  interfere  with  the 
effects  of  the  latter.  Three  leaves,  after  being  immersed  for  20  m. 
in  the  sugar  solution,  were  placed  in  a solution  of  carbonate  of 
ammonia  (one  part  to  218  of  water) ; in  2 m.  or  3 m.  the  glands 
were  blackened,  and  after  7 m.  the  tentacles  were  considerably 
inflected,  so  that  the  solution  of  sugar,  though  it  delayed  the 
action  of  the  phosphate,  did  not  delay  that  of  the  carbonate. 
Immersion  in  a similar  solution  of  gum  arabic  for  20  m.  had  no 
retarding  action  on  the  phosphate.  Three  leaves  were  left  for 
20  m.  in  a mixture  of  one  part  of  alcohol  to  seven  parts  of  water 


214 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX 


and  then  placed  in  the  phosphate  solution  : in  2 hrs.  15  m.  there 
was  a trace  of  inflection  in  one  leaf,  and  in  5 hrs.  30  m.  a second 
was  slightly  affected;  the  inflection  subsequently  increased, 
though  slowly.  Hence  diluted  alcohol,  which,  as  we  shall  see,  is 
hardly  at  all  poisonous,  plainly  retards  the  subsequent  action  of 
the  phosphate. 

It  was  shown  in  the  last  chapter  that  leaves  which  did  not 
become  inflected  by  nearly  a day’s  immersion  in  solutions  of 
various  salts  and  acids  behaved  very  differently  from  one  an- 
other when  subsequently  placed  in  the  phosphate  solution.  I 
here  give  a table  summing  up  the  results. 


Name  of  the  Salts  and 
Acids  in  Solution. 

Period  of 
Immersion 
of  the 
Leaves  in 
Solutions 
of  one  part 
to  437  of 
water. 

Effects  produced  on  the  Leaves  by  their  subse- 
quent Immersion  for  stated  periods  in  a 
Solution  of  one  part  of  phosphate  of 
ammonia  to  8750  of  water,  or  1 gr.  to 
20  oz. 

Rubidium  chloride  . 

22  hrs. 

After  30  m.  strong  inflection  of  the 
tentacles. 

Potassium  carbonate 

20  m. 

Scarcely  any  inflection  until  5 hrs. 
had  elapsed. 

Calcium  acetate 

24  hrs. 

After  24  hrs.  very  slight  inflection. 

Calcium  nitrate . 

24  hrs. 

Do.  do. 

Magnesium  acetate. 

22  hrs. 

Some  slight  inflection,  which  became 
well  pronounced  in  24  hrs. 

Magnesium  nitrate . 

22  hrs. 

After  4 hrs.  30  m.  a fair  amount  of 
inflection,  which  never  increased. 

Magnesium  chloride 

22  hrs. 

After  a few  minutes  great  inflection ; 
after  4 hrs.  all  four  leaves  with  almost 
every  tentacle  closely  inflected. 

Barium  acetate  . 

22  hrs. 

After  24  hrs.  two  leaves  out  of  four 
slightly  inflected. 

Barium  nitrate  . 

22  hrs. 

After  30  m.  one  leaf  greatly,  and  two 
others  moderately,  inflected ; they 
remained  thus  for  24  hrs. 

Strontium  acetate  . 

22  hrs. 

After  25  m.  two  leaves  greatly  in- 
flected; after  8 hrs.  a third  leaf 
moderately,  and  the  fourth  very 
slightly,  inflected.  All  four  thus 
remained  for  24  hrs. 

Strontium  nitrate  . 

22  hrs. 

After  8 hrs.  three  leaves  out  of  five 
moderately  infiected ; after  24  hrs. 
all  five  in  this  state;  but  not  one 
closely  inflected. 

Aluminium  chloride 

24  hrs. 

Three  leaves  which  had  either  been 
slightly  or  not  at  all  affected  by  the 
chloride  became  after  7 hrs.  30  m 
rather  closely  inflected. 

Chap.  IX.  EFFECTS  OF  PREVIOUS  IMMERSION. 


215 


Name  of  the  Salts  and 
Acids  in  Solution. 

Period  of 
Immersion 
of  the 
Leaves  in 
Solutions 
of  one  part 
to  437  of 
water. 

Effects  produced  on  the  Leaves  by  their  sub- 
sequent Immersion  for  stated  periods  in  a 
Solution  of  one  part  of  phosphate  of 
ammonia  to  8750  of  water,  or  1 gr.  to 
20  oz. 

Aluminium  nitrate . 

24  hrs. 

After  25  hrs.  slight  and  doubtful  effect. 

Lead  chloride  . 

23  hrs. 

After  24  hrs.  two  leaves  somewhat 
inflected,  the  third  very  little ; and 
thus  remained. 

Manganese  chloride 

22  hrs. 

After  48  hrs.  not  the  least  inflection. 

Lactic  acid  . 

48  hrs. 

After  24  hrs.  a trace  of  inflection  in 
a few  tentacles,  the  glands  of 
which  had  not  been  killed  by  the 
acid. 

Tannic  acid  . 

24  hrs. 

After  24  hrs.  no  inflection. 

Tartaric  acid 

24  hrs. 

Do.  do. 

Citric  acid  . 

24  hrs. 

After  50  m.  tentacles  decidedly  in- 
flected, and  after  5 hrs.  strongly 
inflected ; so  remained  for  the  next 
24  hrs. 

Formic  acid  . 

22  hrs. 

Not  observed  until  24  hrs.  had  elapsed ; 
tentacles  considerably  inflected,  and 
protoplasm  aggregated. 

In  a large  majority  of  these  twenty  cases,  a varying  degree  of 
inflection  was  slowly  caused  by  the  phosphate.  In  four  cases, 
however,  the  inflection  was  rapid,  occurring  in  less  than  half  an 
hour  or  at  most  in  50  m.  In  three  cases  the  phosphate  did  not 
produce  the  least  effect.  Now  what  are  we  to  infer  from  these 
facts?  We  know  from  ten  trials  that  immersion  in  distilled 
water  for  24  hrs.  prevents  the  subsequent  action  of  the  phos- 
phate solution.  It  would,  therefore,  appear  as  if  the  solutions  of 
chloride  of  manganese,  tannic  and  tartaric  acids,  which  are  not 
poisonous,  acted  exactly  like  water,  for  the  phosphate  produced 
no  effect  on  the  leaves  which  had  been  previously  immersed 
in  these  three  solutions.  The  majority  of  the  other  solutions 
behaved  to  a certain  extent  like  water,  for  the  phosphate  pro- 
duced, after  a considerable  interval  of  time,  only  a shght  effect. 
On  the  other  hand,  the  leaves  w^hich  had  been  immersed  in  the 
solutions  of  the  chloride  of  rubidium  and  magnesium,  of  acetate 
of  strontium,  nitrate  of  barium,  and  citric  acid,  were  quickly 
acted  on  by  the  phosphate.  Now  was  water  absorbed  from  these 
five  weak  solutions,  and  yet,  owing  to  the  presence  of  the  salts, 
did  not  prevent  the  subsequent  action  of  the  phosphate?  Or 


216 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


may  we  not  suppose*  tliat  the  interstices  of  the  walls  of 
the  glands  were  blocked  up  with  the  molecules  of  these  five 
substances,  so  that  they  were  rendered  impermeable  to  water; 
for  had  water  entered,  w^e  know  from  the  ten  trials  that  the 
phosphate  would  not  afterwards  have  produced  any  effect  ? It 
further  appears  that  the  molecules  of  the  carbonate  of  ammonia 
can  quickly  pass  into  glands  which,  from  having  been  immersed 
for  20  m.  in  a weak  solution  of  sugar,  either  absorb  the  phos- 
phate very  slowly  or  are  acted  on  by  it  very  slowly.  On  the 
other  hand,  glands,  however  they  may  have  been  treated,  seem 
easily  to  permit  the  subsequent  entrance  of  the  molecules  of 
carbonate  of  ammonia.  Thus  leaves  which  had  been  immersed 
in  a solution  (of  one  part  to  437  of  water)  of  nitrate  of  potas- 
sium for  48  hrs. — of  sulphate  of  potassium  for  24  hrs. — and  of 
the  chloride  of  potassium  for  25  hrs. — on  being  placed  in  a 
solution  of  one  part  of  carbonate  of  ammonia  to  218  of  water, 
had  their  glands  immediately  blackened,  and  after  1 hr.  their 
tentacles  somewhat  inflected,  and  the  protoplasm  aggregated. 
But  it  would  be  an  endless  task  to  endeavour  to  ascertain 
the  wonderfully  diversified  effects  of  various  solutions  on 
Drosera. 

Alcohol  (one  part  to  seven  of  water). — It  has  already  been  shown 
that  half-minims  of  this  strength  placed  on  the  discs  of  leaves 
do  not  cause  any  inflection ; and  that  when  two  days  afterwards 
the  leaves  were  given  bits  of  meat,  they  became  strongly  in- 
flected. Four  leaves  were  immersed  in  this  mixture,  and  two  of 
them  after  30  m.  were  brushed  with  a camel-hair  brush,  like  the 
leaves  in  the  solution  of  camphor,  but  this  produced  no  effect. 


* See  Dr.  M.  Traube’s  curious 
experiments  on  the  production  of 
artificial  cells,  and  on  their  per- 
meability to  various  salts,  de- 
scribed in  his  papers : “ Experi- 
mente  zur  Theorie  der  Zellenbil- 
dung  und  Endosmose,”  Breslau, 
1866 ; and  “ Experimente  zur 
physicalischen  Erklarung  der  Bil- 
dung  der  Zellhaut,  ihres  Wachs- 
thums  durch  Intussusception,” 
Breslau,  1874.  These  researches 
perhaps  explain  my  results.  Dr. 
Traube  commonly  employed  as  a 
membrane  the  precipitate  formed 
when  tannic  acid  comes  into  con- 
tact with  a solution  of  gelatine. 


By  allowing  a precipitation  of 
sulphate  of  barium  to  take  place 
at  the  same  time,  the  membrane 
becomes  “infiltrated”  with  this 
salt;  and  in  consequence  of  the 
intercalation  of  molecules  of  sul- 
phate of  barium  among  those  of 
the  gelatine  precipitate,  the  mole- 
cular interstices  in  the  membrane 
are  made  smaller.  In  this  altered 
condition,  the  membrane  no  longer 
allows  the  passage  through  it  of 
either  sulphate  of  ammonia  or 
nitrate  of  barium,  though  it  re- 
tains its  permeability  for  water 
and  chloride  of  ammonia. 


Chap.  IX. 


VAPOUR  OF  CHLOROFORM. 


217 


Nor  did  these  four  leaves,  on  being  left  for  24  hrs.  in  the  diluted 
alcohol,  undergo  any  inflection.  They  were  then  removed ; one 
being  placed  in  an  infusion  of  raw  meat,  and  bits  of  meat  on 
the  discs  of  the  other  three,  with  their  stalks  in  water.  Next 
day  one  seemed  a little  injured,  whilst  two  others  showed  merely 
a trace  of  inflection.  We  must,  however,  bear  in  mind  that 
immersion  for  24  hrs.  in  water  prevents  leaves  from  clasping 
meat.  Hence  alcohol  of  the  above  strength  is  not  poisonous,  nor 
does  it  stimulate  the  leaves  like  camphor  does. 

The  vapour  of  alcohol  acts  differently.  A plant  having  three 
good  leaves  was  left  for  25  m.  under  a receiver  holding  19  oz. 
with  sixty  minims  of  alcohol  in  a watch-glass.  No  movement 
ensued,  but  some  few  of  the  glands  were  blackened  and 
shrivelled,  whilst  many  became  quite  pale.  These  were  scattered 
over  all  the  leaves  in  the  most  irregular  manner,  reminding  me 
of  the  manner  in  which  the  glands  were  affected  by  the  vapour 
of  carbonate  of  ammonia.  Immediately  on  the  removal  of  the 
receiver  particles  of  raw  meat  were  placed  on  many  of  the  glands, 
those  which  retained  their  proper  colour  being  chiefly  selected. 
But  not  a single  tentacle  was  inflected  during  the  next  4 hrs. 
After  the  first  2 hrs.  the  glands  on  all  the  tentacles  began  to 
dry;  and  next  morning,  after  22  hrs.,  all  three  leaves  appeared 
almost  dead,  with  their  glands  dry ; the  tentacles  on  one  leaf 
alone  being  partially  inflected. 

A second  plant  was  left  for  only  5 m.  with  some  alcohol  in  a 
watch-glass,  under  a 12-oz.  receiver,  and  particles  of  meat  were 
then  placed  on  the  glands  of  several  tentacles.  After  10  m. 
some  of  them  began  to  curve  inwards,  and  after  55  m.  nearly 
all  were  considerably  inflected ; but  a few  did  not  move.  Some 
anBesthethic  effect  is  here  probable,  but  by  no  means  certain. 
A third  plant  was  also  left  for  5 m.  under  the  same  small  vessel, 
with  its  whole  inner  surface  wetted  with  about  a dozen  drops  of 
alcohol.  Particles  of  meat  were  now  placed  on  the  glands  of 
several  tentacles,  some  of  which  first  began  to  move  in  25  m. ; 
after  40  m.  most  of  them  were  somewhat  inflected,  and  after 
1 hr.  10  m.  almost  all  were  considerably  inflected.  From  their 
slow  rate  of  movement  there  can  be  no  doubt  that  the  glands  of 
these  tentacles  had  been  rendered  insensible  for  a time  by 
exposure  during  5 m.  to  the  vapour  of  alcohol. 

VajpouT  of  ChlorofoTm.~T\\Q  action  of  this  vapour  on  Drosera 
is  very  variable,  depending,  I suppose,  on  the  constitution  or  age 
of  the  plant,  or  on  some  unknown  condition.  It  sometimes 
causes  the  tentacles  to  move  with  extraordinary  rapidity,  and 
sometimes  produces  no  such  effect.  The  glands  are  sometimes 


218 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


rendered  for  a time  insensible  to  the  action  of  raw  meat,  but 
sometimes  are  not  thus  affected,  or  in  a yery  slight  degree.  A 
plant  recovers  from  a small  dose,  but  is  easily  killed  by  a larger 
one. 

A plant  was  left  for  30  m.  under  a bell-glass  holding 
19  fluid  oz.  (539*6  ml.)  with  eight  drops  of  chloroform,  and 
before  the  cover  was  removed,  most  of  the  tentacles  became 
much  inflected,  though  they  did  not  reach  the  centre.  After 
the  cover  was  removed,  bits  of  meat  were  placed  on  the  glands 
of  several  of  the  somewhat  incurved  tentacles;  these  glands 
were  found  much  blackened  after  6 hrs.  30  m.,  but  no  further 
movement  ensued.  After  21  hrs.  the  leaves  appeared  almost 
dead. 

A smaller  bell-glass,  holding  12  fluid  oz.  (340*8  ml.),  was  now 
employed,  and  a plant  was  left  for  90  s.  under  it,  with  only 
two  drops  of  chloroform.  Immediately  on  the  removal  of  the 
glass  all  the  tentacles  curved  inwards  so  as  to  stand  perpen- 
dicularly up ; and  some  of  them  could  actually  be  seen  moving 
with  extraordinary  quickness  by  little  starts,  and  therefore  in 
an  unnatural  manner;  but  they  never  reached  the  centre. 
After  22  hrs.  they  fully  re-expanded,  and  on  meat  being  placed 
on  their  glands,  or  when  roughly  touched  by  a needle,  they 
promptly  became  inflected;  so  that  these  leaves  had  not  been 
in  the  least  injured. 

Another  plant  was  placed  under  the  same  small  bell-glass 
with  three  drops  of  chloroform,  and  before  two  minutes  had 
elapsed,  the  tentacles  began  to  curl  inwards  with  rapid  little 
jerks.  The  glass  was  then  removed,  and  in  the  course  of  two 
or  three  additional  minutes  almost  every  tentacle  reached  the 
centre.  On  several  other  occasions  the  vapour  did  not  excite 
any  movement  of  this  kind. 

There  seems  also  to  be  great  variability  in  the  degree  and 
manner  in  which  chloroform  renders  the  glands  insensible  to  the 
subsequent  action  of  meat.  In  the  plant  last  referred  to,  which 
had  been  exposed  for  2 m.  to  three  drops  of  chloroform,  some 
few  tentacles  curved  up  only  to  a perpendicular  position,  and 
particles  of  meat  were  placed  on  their  glands;  this  caused 
them  in  5 m.  to  begin  moving,  but  they  moved  so  slowly  that 
they  did  not  reach  the  centre  until  1 hr.  30  m.  had  elapsed. 
Another  plant  was  similarly  exposed,  that  is,  for  2 m.  to  three 
drops  of  chloroform,  and  on  particles  of  meat  being  placed  on 
the  glands  of  several  tentacles,  which  had  curved  up  into  a 
perpendicular  position,  one  of  these  began  to  bend  in  8 m.,  but 
afterwards  moved  very  slowly ; whilst  none  of  the  other  tentacles 


Chap.  IX. 


VAPOUR  OF  ETHER. 


219 


moved  for  the  next  40  m.  Nevertheless,  in  1 hr.  45  m.  from  the 
time  when  the  bits  of  meat  had  been  given,  all  the  tentacles 
reached  the  centre.  In  this  case  some  slight  anaesthetic  effect 
apparently  had  been  produced.  On  the  following  day  the  plant 
had  perfectly  recovered. 

Another  plant  bearing  two  leaves  was  exposed  for  2 m.  under 
the  19-oz.  vessel  to  two  drops  of  chloroform ; it  was  then  taken 
out  and  examined;  again  exposed  for  2 m.  to  two  drops; 
taken  out,  and  re-exposed  for  3 m.  to  three  drops ; so  that 
altogether  it  was  exposed  alternately  to  the  air  and  during 
7 m.  to  the  vapour  of  seven  drops  of  chloroform.  Bits  of  meat 
were  now  placed  on  thirteen  glands  on  the  two  leaves.  On  one 
of  these  leaves,  a single  tentacle  first  began  moving  in  40  m., 
and  two  others  in  54  m.  On  the  second  leaf  some  tentacles 
first  moved  in  1 hr.  11  m.  After  2 hrs.  many  tentacles  on  both 
leaves  were  inflected ; but  none  had  reached  the  centre  within 
this  time.  In  this  case  there  could  not  be  the  least  doubt  that 
the  chloroform  had  exerted  an  ansesthetic  influence  on  the 
leaves. 

On  the  other  hand,  another  plant  was  exposed  under  the  same 
vessel  for  a much  longer  time,  viz.  20  m.,  to  twice  as  much 
chloroform.  Bits  of  meat  were  then  placed  on  the  glands  of 
many  tentacles,  and  all  of  them,  with  a single  exception,  reached 
the  centre  in  from  13  m.  to  14  m.  In  this  case,  little  or  no 
anaesthetic  effect  had  been  produced  ; and  how  to  reconcile 
these  discordant  results,  I know  not. 

Vapour  of  Sulphuric  Ether. — A plant  was  exposed  for  80  m.  to 
thirty  minims  of  this  ether  in  a vessel  holding  19  oz. ; and  bits 
of  raw  meat  were  afterwards  placed  on  many  glands  which  had 
become  pale-coloured  ; but  none  of  the  tentacles  moved.  After 
6 hrs.  30  m.  the  leaves  appeared  sickly,  and  the  discal  glands 
were  almost  dry.  By  the  next  morning  many  of  the  tentacles 
were  dead,  as  were  all  those  on  which  meat  had  been  placed ; 
showing  that  matter  had  been  absorbed  from  the  meat  which 
had  increased  the  evil  effects  of  the  vapour.  After  four  days 
the  plant  itself  died.  Another  plant  was  exposed  in  the  same 
vessel  for  15  m.  to  forty  minims.  One  young,  small,  and 
tender  leaf  had  all  its  tentacles  inflected,  and  seemed  much 
injured.  Bits  of  raw  meat  were  placed  on  several  glands  on 
two  other  and  older  leaves.  These  glands  became  dry  after 
6 hrs.,  and  seemed  injured ; the  tentacles  never  moved,  except- 
ing one  which  was  ultimately  a little  inflected.  The  glands  of 
the  other  tentacles  continued  to  secrete,  and  appeared  uninjured, 
but  the  whole  plant  after  three  days  became  very  sickly. 


220 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


In  the  two  foregoing  experiments  the  doses  were  evidently  too 
large  and  poisonous.  With  weaker  doses,  the  anaesthetic  effect 
was  variable,  as  in  the  case  of  chloroform.  A plant  was  exposed 
for  5 m.  to  ten  drops  under  a 12-oz.  vessel,  and  bits  of  meat  were 
then  placed  on  many  glands.  None  of  the  tentacles  thus  treated 
began  to  move  in  a decided  manner  until  40  m.  had  elapsed ; but 
then  some  of  them  moved  very  quickly,  so  that  two  reached  the 
centre  after  an  additional  interval  of  only  10  m.  In  2 hrs.  12  m. 
from  the  time  when  the  meat  was  given,  all  the  tentacles  reached 
the  centre.  Another  plant,  with  two  leaves,  was  exposed  in  the 
same  vessel  for  5 m.  to  a rather  larger  dose  of  ether,  and  bits  of 
meat  were  placed  on  several  glands.  In  this  case  one  tentacle 
on  each  leaf  began  to  bend  in  5 m. ; and  after  12  m.  two  tentacles 
on  one  leaf,  and  one  on  the  second  leaf,  reached  the  centre.  In 
30  m.  after  the  meat  had  been  given,  all  the  tentacles,  both  those 
with  and  without  meat,  were  closely  inflected ; so  that  the  ether 
apparently  had  stimulated  these  leaves,  causing  all  the  tentacles 
to  bend. 

Vapour  of  Nitric  Ether, — This  vapour  seems  more  injurious  than 
that  of  sulphuric  ether.  A plant  was  exposed  for  5 m.  in  a 12- 
oz.  vessel  to  eight  drops  in  a watch-glass,  and  I distinctly  saw  a 
few  tentacles  curling  inwards  before  the  glass  was  removed. 
Immediately  afterwards  bits  of  meat  were  placed  on  three 
glands,  but  no  movement  ensued  in  the  course  of  18  m.  The 
same  plant  was  placed  again  under  the  same  vessel  for  16  m. 
with  ten  drops  of  the  ether.  None  of  the  tentacles  moved, 
and  next  morning  those  with  the  meat  were  still  in  the  same 
position.  After  48  hrs.  one  leaf  seemed  healthy,  but  the  others 
were  much  injured. 

Another  plant,  having  two  good  leaves,  was  exposed  for  6 m. 
under  a 19-oz.  vessel  to  the  vapour  from  ten  minims  of  the 
ether,  and  bits  of  meat  were  then  placed  on  the  glands  of  many 
tentacles  on  both  leaves.  After  36  m.  several  of  them  on  one 
leaf  became  inflected,  and  after  1 hr.  almost  all  the  tentacles, 
those  with  and  without  meat,  nearly  reached  the  centre.  On 
the  other  leaf  the  glands  began  to  dry  in  1 hr.  40  m.,  and  after 
several  hours  not  a single  tentacle  was  inflected;  but  by  the 
next  morning,  after  21  hrs.,  many  were  inflected,  though  they 
seemed  much  injured.  In  this  and  the  previous  experiment, 
it  is  doubtful,  owing  to  the  injury  which  the  leaves  had  suffered, 
whether  any  anaesthetic  effect  had  been  produced. 

A third  plant,  having  two  good  leaves,  was  exposed  for  only 
4 m.  in  the  19-oz.  vessel  to  the  vapour  from  six  drops.  Bits  of 
meat  were  then  placed  on  the  glands  of  seven  tentacles  on  the 


Chap.  IX. 


CAKBONIC  ACID. 


221 


same  leaf.  A single  tentacle  moved  after  1 hr.  23  m. ; after 

2 hrs.  3 m.  several  were  inflected ; and  after  3 hrs.  3 m.  all  the 
seven  tentacles  with  meat  were  well  inflected.  From  the  slow- 
ness of  these  movements  it  is  clear  that  this  leaf  had  been 
rendered  insensible  for  a time  to  the  action  of  the  meat.  A 
second  leaf  was  rather  differently  affected;  bits  of  meat  were 
placed  on  the  glands  of  five  tentacles,  three  of  which  were 
slightly  inflected  in  28  m.;  after  1 hr.  21  m.  one  reached  the 
centre,  but  the  other  two  were  still  only  slightly  inflected ; after 

3 hrs.  they  were  much  more  inflected;  but  even  after  5 hrs. 
16  m.  all  five  had  not  reached  the  centre.  Although  some  of 
the  tentacles  began  to  move  moderately  soon,  they  afterwards 
moved  with  extreme  slowness.  By  next  morning,  after  20  hrs., 
most  of  the  tentacles  on  both  leaves  were  closely  inflected,  but 
not  quite  regularly.  After  48  hrs.  neither  leaf  appeared  injured, 
though  the  tentacles  were  still  inflected;  after  72  hrs.  one 
was  almost  dead,  whilst  the  other  was  re-expanding  and 
recovering. 

Carbonic  Acid. — A plant  was  placed  under  a 122-oz.  bell-glass 
filled  with  this  gas  and  standing  over  water ; but  I did  not  make 
sufficient  allowance  for  the  absorption  of  the  gas  by  the  water, 
so  that  towards  the  latter  part  of  the  experiment  some  air  was 
drawn  in.  After  an  exposure  of  2 hrs.  the  plant  was  removed, 
and  bits  of  raw  meat  placed  on  the  glands  of  three  leaves.  One  of 
these  leaves  hung  a little  down,  and  was  at  first  partly  and  soon 
afterwards  completely  covered  by  the  water,  which  rose  within 
the  vessel  as  the  gas  was  absorbed.  On  this  latter  leaf  the 
tentacles,  to  which  meat  had  been  given,  became  well  inflected 
in  2 m.  30  s.,  that  is,  at  about  the  normal  rate ; so  that  until 
I remembered  that  the  leaf  had  been  protected  from  the  gas, 
and  might  perhaps  have  absorbed  oxygen  from  the  water 
which  was  continually  drawn  inwards,  I falsely  concluded  that 
the  carbonic  acid  had  produced  no  effect.  On  the  other  two 
leaves,  the  tentacles  with  meat  behaved  very  differently  from 
those  on  the  first  leaf ; two  of  them  first  began  to  move  slightly 
in  1 hr.  50  m.,  always  reckoning  from  the  time  when  the  meat 
was  placed  on  the  glands — were  plainly  inflected  in  2 hrs. 
22  m. — and  in  3 hrs.  22  m.  reached  the  centre.  Three  other 
tentacles  did  not  begin  to  move  until  2 hrs.  20  m.  had  elapsed, 
but  reached  the  centre  at  about  the  same  time  with  the  others, 
viz.  in  3 hrs.  22  m. 

This  experiment  was  repeated  several  times  with  nearly  the 
same  results,  excepting  that  the  interval  before  the  tentacles 
began  to  move  varied  a Little.  I will  give  only  one  other  case. 


^22 


DKOSERA  ROTUNDIFOLIA. 


Chap.  IX. 


A plant  was  exposed  in  the  same  vessel  to  the  gas  for  45  m.,  and 
bits  of  meat  were  then  placed  on  four  glands.  But  the  ten- 
tacles did  not  move  for  1 hr.  40  m. ; after  2 hrs.  30  m.  all  four 
were  well  inflected,  and  after  3 hrs.  reached  the  centre. 

The  following  singular  phenomenon  sometimes,  but  by  no 
means  always,  occurred.  A plant  was  immersed  for  2 hrs.,  and 
bits  of  meat  were  then  placed  on  several  glands.  In  the  course 
of  13  m.  all  the  submarginal  tentacles  on  one  leaf  became  con- 
siderably inflected ; those  with  the  meat  not  in  the  least  degree 
more  than  the  others.  On  a second  leaf,  which  was  rather 
old,  the  tentacles  with  meat,  as  well  as  a few  others,  were 
moderately  inflected.  On  a third  leaf  all  the  tentacles  were 
closely  inflected,  though  meat  had  not  been  placed  on  any  of 
the  glands.  This  movement,  I presume,  may  be  attributed  to 
excitement  from  the  absorption  of  oxygen.  The  last-mentioned 
leaf,  to  which  no  meat  had  been  given,  was  fully  re-expanded 
after  24  hrs.;  whereas  the  two  other  leaves  had  all  their  ten- 
tacles closely  inflected  over  the  bits  of  meat  which  by  this  time 
had  been  carried  to  their  centres.  Thus  these  three  leaves 
had  perfectly  recovered  from  the  effects  of  the  gas  in  the  course 
of  24  hrs. 

On  another  occasion  some  fine  plants,  after  having  been  left 
for  2 hrs.  in  the  gas,  were  immediately  given  bits  of  meat  in  the 
usual  manner,  and  on  their  exposure  to  the  air  most  of  their 
tentacles  became  in  12  m.  curved  into  a vertical  or  sub-vertical 
position,  but  in  an  extremely  irregular  manner ; some  only  on  one 
side  of  the  leaf  and  some  on  the  other.  They  remained  in  this 
position  for  some  time ; the  tentacles  with  the  bits  of  meat  not 
having  at  first  moved  more  quickly  or  farther  inwards  than  the 
others  without  meat.  But  after  2 hrs.  20  m.  the  former  began 
to  move,  and  steadily  went  on  bending  until  they  reached  the 
centre.  Next  morning,  after  22  hrs.,  all  the  tentacles  on  these 
leaves  were  closely  clasped  over  the  meat  which  had  been  carried 
to  their  centres ; whilst  the  vertical  and  sub- vertical  tentacles  on 
the  other  leaves  to  which  no  meat  had  been  given  had  fully 
re-expanded.  Judging,  however,  from  the  subsequent  action  of 
a weak  solution  of  carbonate  of  ammonia  on  one  of  these  latter 
leaves,  it  had  not  perfectly  recovered  its  excitability  and  power 
of  movement  in  22  hrs. ; but  another  leaf,  after  an  additional 
24  hrs.,  had  completely  recovered,  judging  from  the  manner  in 
which  it  clasped  a fly  placed  on  its  disc. 

1 will  give  only  one  other  experiment.  After  the  exposure  of 
a plant  for  2 hrs.  to  the  gas,  one  of  its  leaves  was  immersed  in 
a rather  strong  solution  of  carbonate  of  ammonia,  together  with 


Chap.  IX. 


SUMMARY  OF  THE  CHAPTER. 


223 


a fresh  leaf  from  another  plant.  The  latter  had  most  of  its 
tentacles  strongly  inflected  within  30  m. ; whereas  the  leaf  which 
had  been  exposed  to  the  carbonic  acid  remained  for  24  hrs.  in 
the  solution  without  undergoing  any  inflection,  with  the  excep- 
tion of  two  tentacles.  This  leaf  had  been  almost  completely 
paralysed,  and  was  not  able  to  recover  its  sensibility  whilst  still 
in  the  solution,  which  from  having  been  made  with  distilled 
water  probably  contained  little  oxygen. 

Concluding  Remarlcs  on  the  Effects  of  the  foregoing 
Agents, — As  the  glands,  when  excited,  transmit  some 
influence  to  the  surrounding  tentacles,  causing  them 
to  bend  and  their  glands  to  pour  forth  an  increased 
amount  of  modifled  secretion,  I was  anxious  to 
ascertain  whether  the  leaves  included  any  element 
having  the  nature  of  nerve-tissue,  which,  though 
not  continuous,  served  as  the  channel  of  transmission. 
This  led  me  to  try  the  several  alkaloids  and  other 
substances  which  are  known  to  exert  a powerful  in- 
fluence on  the  nervous  system  of  animals.  I was  at 
first  encouraged  in  my  trials  by  finding  that  strych- 
nine, digitaline,  and  nicotine,  which  all  act  on  the 
nervous  system,  were  poisonous  to  Drosera,  and  caused 
a certain  amount  of  inflection.  Hydrocyanic  acid, 
again,  which  is  so  deadly  a poison  to  animals,  caused 
rapid  movement  of  the  tentacles.  ^ But  as  several  in- 
nocuous acids,  though  much  diluted,  such  as  benzoic, 
acetic,  &c.,  as  well  as  some  essential  oils,  are  ex- 
tremely poisonous  to  Drosera,  and  quickly  cause 
strong  inflection,  it  seems  probable  that  strychnine, 
nicotine,  digitaline,  and  hydrocyanic  acid,  excite  in- 
flection by  acting  on  elements  in  no  way  analogous 
to  the  nerve-cells  of  animals.  ^ If  elements  of  this 
latter  nature  had  been  present  in  the  leaves,  it  might 
have  been  expected  that  morphia,  hyoscyamus,  atro- 
pine, veratrine,  colchicine,  curare,  and  diluted  alcohol 
would  have  produced  some  marked  effect;  whereas 


224 


DROkSERA  rotundifolia. 


Chap.  IX. 


these  substances  are  not  poisonous  and  have  no  power, 
or  only  a very  slight  one,  of  inducing  inflection.  It 
should,  however,  be  observed  that  curare,  colchicine, 
and  veratrine  are  muscle-poisons — that  is,  act  on 
nerves  having  some  special  relation  with  the  muscles, 
and,  therefore,  could  not  be  expected  to  act  on  Drosera. 
The  poison  of  the  cobra  is  most  deadly  to  animals, 
by  paralysing  their  nerve-centres,*  yet  is  not  in  the 
least  so  to  Drosera,  though  quickly  causing  strong 
inflection. 

Notwithstanding  the  foregoing  facts,  which  show 
how  widely  different  is  the  effect  of  certain  substances 
on  the  health  or  life  of  animals  and  of  Drosera,  yet 
there  exists  a certain  degree  of  parallelism  in  the 
action  of  certain  other  substances.  We  have  seen  that 
this  holds  good  in  a striking  manner  with  the  salts  of 
sodium  and  potassium.  Again,  various  metallic  salts 
and  acids,  namely  those  of  silver,  mercury,  gold,  tin, 
arsenic,  chromium,  copper,  and  platina,  most  or  all  of 
which  are  highly  poisonous  to  animals,  are  equally  so 
/ to  Drosera.  But  it  is  a singular  fact  that  the  chloride 
of  lead  and  two  salts  of  barium  were  not  poisonous  to 
this  plant.  It  is  an  equally  strange  fact,  that,  though 
acetic  and  propionic  acids  are  highly  poisonous,  their 
ally,  formic  acid,  is  not  so ; and  that,  whilst  certain 
vegetable  acids,  namely  oxalic,  benzoic,  &c.,  are 
poisonous  in  a high  degree,  gallic,  tannic,  tartaric,  and 
malic  (all  diluted  to  an  equal  degree)  are  not  so. 
Malic  acid  induces  inflection,  whilst  the  three  other 
just  named  vegetable  acids  have  no  such  power.  But 
a pharmacopoeia  would  be  requisite  to  describe  the 
diversified  effects  of  various  substances  on  Drosera.f 

* Dr.  Fayrer,  ‘The  Thahalo-  cyanic,  and  chromic  acids,  ace- 
phidia  of  India,’  1872,  p.  4.  tate  of  strychnine,  and  vapour  of 

t Seeing  that  acetic,  hydro-  ether,  are  poisonous  to  Drosera, 


Chap.  IX. 


SUMMARY  OF  THE  CHAPTER. 


225 


Of  the  alkaloids  and  their  salts  which  were  tried, 
several  had  not  the  least  power  of  inducing  inflection ; 
others,  which  were  certainly  absorbed,  as  shown  by  the 
changed  colour  of  the  glands,  had  but  a very  mode- 
rate power  of  this  kind;  others,  again,  such  as  the 
acetate  of  quinine  and  digitaline,  caused  strong  in- 
flection. 

The  several  substances  mentioned  in  this  chapter 
affect  the  colour  of  the  glands  very  differently.  These 
often  become  dark  at  first,  and  then  very  pale  or 
white,  as  was  conspicuously  the  case  with  glands 
subjected  to  the  poison  of  the  cobra  and  citrate  of 
strychnine.  In  other  cases  they  are  from  the  first 
rendered  white,  as  with  leaves  placed  in  hot  water  and 
several  acids ; and  this,  I presume,  is  the  result  of  the 
coagulation  of  the  albumen.  On  the  same  leaf  some 
glands  become  white  and  others  dark-coloured,  as 
occurred  with  leaves  in  a solution  of  the  sulphate  of 
quinine,  and  in  the  vapour  of  alcohol.  Prolonged  im- 
mersion in  nicotine,  curare,  and  even  water,  blackens 
the  glands ; and  this,  I believe,  is  due  to  the  aggre- 
gation of  the  protoplasm  within  their  cells.  Yet 
curare  caused  very  little  aggregation  in  the  cells  of 
the  tentacles,  whereas  nicotine  and  sulphate  of  quinine 
induced  strongly  marked  aggregation  down  their 
bases.  The  aggregated  masses  in  leaves  which  had 
been  immersed  for  3 hrs.  15  m.  in  a saturated  solu- 
tion of  sulphate  of  quinine  exhibited  incessant 


it  is  remarkable  that  Dr.  Ransom 
(‘ Philosoph.  Transact.*  1867,  p. 
480),  who  used  much  stronger 
solutions  of  these  substances  than 
I did,  states  “ that  the  rhythmic 
contractility  of  the  yolk  (of  the 
ova  of  the  pike)  is  not  materially 
influenced  by  any  of  the  poisons 
used,  which  did  not  act  chemi- 


cally, with  the  exception  of  chloro- 
form and  carbonic  acid.**  I find 
it  stated  by  several  writers  that 
curare  has  no  influence  on  sarcode 
or  protoplasm,  and  we  have  seen 
that,  though  curare  excites  some 
degree  of  inflection,  it  causes  very 
little  aggregation  of  the  proto- 
plasm. 


226 


DROSERA  ROTUNDIFOLIA. 


Chap.  IX. 


changes  of  form,  but  after  24  hrs.  were  motionless ; 
the  leaf  being  flaccid  and.  apparently  dead.  On  the 
other  hand,  with  leaves  subjected  for  48  hrs.  to  a 
strong  solution  of  the  poison  of  the  cobra,  the  proto- 
plasmic masses  were  unusually  active,  whilst  with 
the  higher  animals  the  vibratile  cilia  and  white 
corpuscles  of  the  blood  seem  to  be  quickly  paralysed 
by  this  substance. 

With  the  salts  of  alkalies  and  earths,  the  nature  of 
the  base,  and  not  that  of  the  acid,  determines  their 
physiological  action  on  Drosera,  as  is  likewise  the  case 
with  animals ; but  this  rule  hardly  applies  to  the  salts 
of  quinine  and  strychnine,  for  the  acetate  of  quinine 
causes  much  more  inflection  than  the  sulphate,  and 
both  are  poisonous,  whereas  the  nitrate  of  quinine  is 
not  poisonous,  and  induces  inflection  at  a much  slower 
rate  than  the  acetate.  The  action  of  the  citrate  of 
strychnine  is  also  somewhat  difierent  from  that  of  the 
sulphate. 

Leaves  which  have  been  immersed  for  24  hrs.  in 
water,  and  for  only  20  m.  in  diluted  alcohol,  or  in  a 
weak  solution  of  sugar,  are  afterwards  acted  on  very 
slowly,  or  not  at  all,  by  the  phosphate  of  ammonia, 
though  they  are  quickly  acted  on  by  the  carbonate. 
Immersion  for  20  m.  in  a solution  of  gum  arabic  has 
no  such  inhibitory  power.  The  solutions  of  certain 
salts  and  acids  affect  the  leaves,  with  respect  to  the 
subsequent  action  of  the  phosphate,  exactly  like  water, 
whilst  others  allow  the  phosphate  afterwards  to  act 
quickly  and  energetically.  In  this  latter  case,  the 
interstices  of  the  cell-walls  may  have  been  blocked  up 
by  the  molecules  of  the  salts  first  given  in  solution, 
so  that  water  could  not  afterwards  enter,  though  the 
molecules  of  the  phosphate  could  do  so,  and  those  of 
the  carbonate  still  more  easily. 


Chap.  IX 


SUMMAEY  OF  THE  CHAPTER. 


227 


The  action  of  camphor  dissolved  in  water  is  remark- 
able, for  it  not  only  soon  induces  inflection,  but 
apparently  renders  the  glands  extremely  sensitive  to 
mechanical  irritation ; for  if  they  are  brushed  with  a 
soft  brush,  after  being  immersed  in  the  solution  for 
a short  time,  the  tentacles  begin  to  bend  in  about 
2 m.  It  may,  however,  be  that  the  brushing, 
though  not  a sufficient  stimulus  by  itself,  tends  to 
excite  movement  merely  by  reinforcing  the  direct 
action  of  the  camphor.  The  vapour  of  camphor,  on 
the  other  hand,  serves  as  a narcotic. 

Some  essential  oils,  both  in  solution  and  in  vapour, 
cause  rapid  inflection,  others  have  no  such  power ; 
those  which  I tried  were  all  poisonous. 

Diluted  alcohol  (one  part  to  seven  of  water)  is  not 
poisonous,  does  not  induce  inflection,  nor  increase  the 
sensitiveness  of  the  glands  to  mechanical  irritation. 
The  vapour  acts  as  a narcotic  or  anaesthetic,  and  long 
exposure  to  it  kills  the  leaves. 

The  vapours  of  chloroform,  sulphuric  and  nitric 
ether,  act  in  a singularly  variable  manner  on  different 
leaves,  and  on  the  several  tentacles  of  the  same  leaf. 
This,  I suppose,  is  owing  to  differences  in  the  age  or 
constitution  of  the  leaves,  and  to  whether  certain 
tentacles  have  lately  been  in  action.  That  these 
vapours  are  absorbed  by  the  glands  is  shown  by  their 
changed  colour ; but  as  other  plants  not  furnished 
with  glands  are  affected  by  these  vapours,  it  is 
probable  that  they  are  likewise  absorbed  by  the  sto- 
mata of  Drosera.  They  sometimes  excite  extraordi- 
narily rapid  inflection,  but  this  is  not  an  invariable 
result.  If  allowed  to  act  for  even  a moderately  long 
time,  they  kill  the  leaves ; whilst  a small  dose  acting 
for  only  a short  time  serves  as  a narcotic  or  anaesthetic. 
In  this  case  the  tentacles,  whether  or  not  they  have 


228 


DROSEKA  EOTUNDIFOLIA. 


Chap.  IX. 


become  inflected,  are  not  excited  to  further  move- 
ment by  bits  of  meat  placed  on  the  glands,  until 
some  considerable  time  has  elapsed.  It  is  generally 
believed  that  with  animals  and  plants  these  vapours 
act  by  arresting  oxidation. 

Exposure  to  carbonic  acid  for  2 hrs.,  and  in  one  case 
for  only  45  m.,  likewise  rendered  the  glands  insensible 
for  a time  to  the  powerful  stimulus  of  raw  meat.  The 
leaves,  however,  recovered  their  full  powers,  and  did 
not  seem  in  the  least  injured,  on  being  left  in  the 
air  for  24  or  48  hrs.  We  have  seen  in  the  third 
chapter  that  the  process  of  aggregation  in  leaves  sub- 
jected for  two  hours  to  this  gas  and  then  immersed  in 
a solution  of  the  carbonate  of  ammonia  is  much  re- 
tarded, so  that  a considerable  time  elapses  before  the 
protoplasm  in  the  lower  cells  of  the  tentacles  becomes 
aggregated.  In  some  cases,  soon  after  the  leaves  were 
removed  from  the  gas  and  brought  into  the  air,  the 
tentacles  moved  spontaneously  ; this  being  due,  I pre- 
sume, to  the  excitement  from  the  access  of  oxygen. 
These  inflected  tentacles,  however,  could  not  be  ex- 
cited for  some  time  afterwards  to  any  further  move- 
ment by  their  glands  being  stimulated.  With  other 
irritable  plants  it  is  known*  that  the  exclusion  of 
oxygen  prevents  their  moving,  and  arrests  the  move- 
ments of  the  protoplasm  within  their  cells,  but  this 
arrest  is  a different  phenomenon  from  the  retardation 
of  the  process  of  aggregation  just  alluded  to.  Whether 
this  latter  fact  ought  to  be  attributed  to  the  direct 
action  of  the  carbonic  acid,  or  to  the  exclusion  of 
oxygen,  I know  not. 


Sachs,  * Traite  de  Bot.’  1874,  pp.  846,  1037. 


Chap.  X. 


SENSITIVENESS  OF  THE  LEAVES. 


229 


CHAPTEE  X. 

On  the  Sensitiveness  of  the  Leaves,  and  on  the  Lines  op 
Transmission  op  the  Motor  Impulse. 

Glands  and  summits  of  the  tentacles  alone  sensitive  — Transmission 
of  the  motor  impulse  down  the  pedicels  of  the  tentacles,  and 
across  the  blade  of  the  leaf — Aggregation  of  the  protoplasm, 
a reflex  action  — First  discharge  of  the  motor  impulse  sudden  — 
Direction  of  the  movements  of  the  tentacles  — Motor  impulse 
transmitted  through  the  cellular  tissue  — Mechanism  of  the  move- 
ments— Nature  of  the  motor  impulse  — Ee-expansion  of  the  ten- 
tacles. 

We  have  seen  in  the  previous  chapters  that  many 
widely  different  stimulants,  mechanical  and  chemical, 
excite  the  movement  of  the  tentacles,  as  well  as  of  the 
blade  of  the  leaf ; and  we  must  now  consider,  firstly, 
what  are  the  points  which  are  irritable  or  sensitive, 
and  secondly  how  the  motor  impulse  is  transmitted 
from  one  point  to  another.  The  glands  are  almost 
exclusively  the  seat  of  irritability,  yet  this  irritability 
must  extend  for  a very  short  distance  below  them ; 
for  when  they  were  cut  off  with  a sharp  pair  of 
scissors  without  being  themselves  touched,  the  ten- 
tacles often  became  inflected.  These  headless  ten- 
tacles frequently  re-expanded ; and  when  afterwards 
drops  of  the  two  most  powerful  known  stimulants  were 
placed  on  the  cut-off  ends,  no  effect  was  produced. 
Nevertheless  these  headless  tentacles  are  capable  of 
subsequent  inflection  if  excited  by  an  impulse  sent 
from  the  disc.  I succeeded  on  several  occasions  in 
crushing  glands  between  fine  pincers,  but  this  did 
not  excite  any  movement ; nor  did  raw  meat  and  salts 
of  ammonia,  when  placed  on  such  crushed  glands. 


230 


DEOSEKA  KOTUNDIFOLIA. 


Chap.  X. 


It  is  probable  that  they  were  killed  so  instantly  that 
they  were  not  able  to  transmit  any  motor  impulse ; for 
in  six  observed  cases  (in  two  of  which  however  the 
gland  was  quite  pinched  off)  the  protoplasm  within 
the  cells  of  the  tentacles  did  not  become  aggregated ; 
whereas  in  some  adjoining  tentacles,  which  were 
inflected  from  having  been  roughly  touched  by  the 
pincers,  it  was  well  aggregated.  In  like  manner  the 
protoplasm  does  not  become  aggregated  when  a leaf  is 
instantly  killed  by  being  dipped  into  boiling  water. 
On  the  other  hand,  in  several  cases  in  which  tentacles 
became  inflected  after  their  glands  had  been^cut  off 
with  sharp  scissors,  a distinct  though  moderate  degree 
of  aggregation  supervened. 

The  pedicels  of  the  tentacles  were  roughly  and  re- 
peatedly rubbed;  raw  meat  or  other  exciting  sub- 
stances were  placed  on  them,  both  on  the  upper 
surface  near  the  base  and  elsewhere,  but  no  dis- 
tinct movement  ensued.  Some  bits  of  meat,  after 
being  left  for  a considerable  time  on  the  pedicels, 
were  pushed  upwards,  so  as  just  to  touch  the  glands, 
and  in  a minute  the  tentacles  began  to  bend.  I 
believe  that  the  blade  of  the  leaf  is  not  sensitive  to 
any  stimulant.  I drove  the  point  of  a lancet  through 
the  blades  of  several  leaves,  and  a needle  three  or  four 
times  through  nineteen  leaves  : in  the  former  case 
no  movement  ensued ; but  about  a dozen  of  the  leaves 
which  were  repeatedly  pricked  had  a few  tentacles 
irregularly  inflected.  As,  however,  their  backs  had 
to  be  supported  during  the  operation,  some  of  the 
outer  glands,  as  well  as  those  on  the  disc,  may  have 
been  touched;  and  this  perhaps  sufficed  to  cause  the 
slight  degree  of  movement  observed.  Nitschke*  says 


♦ ‘Bot.  Zeitung,*  1860,  p.  234. 


Chap.  X. 


SENSITIVENESS  OF  THE  LEAVES. 


231 


that  cutting  and  pricking  the  leaf  does  not  excite 
movement.  The  petiole  of  the  leaf  is  quite  insensible. 

The  backs  of  the  leaves  bear  numerous  minute 
papillse,  which  do  not  secrete,  but  have  the  power  of 
absorption.  These  papillae  are,  I believe,  rudiments 
of  formerly  existing  tentacles  together  with  their 
glands.  Many  experiments  were  made  to  ascertain 
whether  the  backs  of  the  leaves  could  be  irritated  in 
any  way,  thirty-seven  leaves  being  thus  tried.  Some 
were  rubbed  for  a long  time  with  a blunt  needle, 
and  drops  of  milk  and  other  exciting  fluids,  raw 
meat,  crushed  flies,  and  various  substances,  placed  on 
others.  These  substances  were  apt  soon  to  become 
dry,  showing  that  no  secretion  had  been  excited. 
Hence  I moistened  them  with  saliva,  solutions  of 
ammonia,  weak  hydrochloric  acid,  and  frequently  with 
the  secretion  from  the  glands  of  other  leaves.  I 
also  kept  some  leaves,  on  the  backs  of  which  exciting 
objects  had  been  placed,  under  a damp  bell-glass ; but 
with  all  my  care  I never  saw  any  true  movement.  I 
was  led  to  make  so  many  trials  because,  contrary  to 
my  previous  experience,  Nitschke  states'^  that,  after 
affixing  objects  to  the  backs  of  leaves  by  the  aid  of 
the  viscid  secretion,  he  rej^eatedly  saw  the  tentacles 
(and  in  one  instance  the  blade)  become  reflexed. 
This  movement,  if  a true  one,  would  be  most  ano- 
malous; for  it  implies  that  the  tentacles  receive  a 
motor  impulse  from  an  unnatural  source,  and  have 
the  power  of  bending  in  a direction  exactly  the 
reverse  of  that  which  is  habitual  to  them ; this  power 
not  being  of  the  least  use  to  the  plant,  as  insects 
cannot  adhere  to  the  smooth  backs  of  the  leaves. 

I have  said  that  no  effect  was  produced  in  the  above 


* ‘ Bot.  Zeitung,'  1860,  p.  437. 


232 


DROSERA  ROTUNDIFOLIA. 


Chap.  X. 


cases ; but  this  is  not  strictly  true,  for  in  three  in- 
stances a little  syrup  was ‘added  to  the  bits  of  raw 
meat  on  the  backs  of  leaves,  in  order  to  keep  them 
damp  for  a time  ; and  after  36  hrs.  there  was  a trace 
of  reflexion  in  the  tentacles  of  one  leaf,  and  cer- 
tainly in  the  blade  of  another.  After  twelve  addi- 
tional hours,  the  glands  began  to  dry,  and  all  three 
leaves  seemed  much  injured.  Four  leaves  were  then 
placed  under  a bell-glass,  with  their  footstalks  in 
water,  with  drops  of  syrup  on  their  backs,  but  without 
any  meat.  Two  of  these  leaves,  after  a day,  had  a few 
tentacles  reflexed.  The  drops  had  now  increased  con- 
siderably in  size,  from  having  imbibed  moisture,  so 
as  to  trickle  down  the  backs  of  the  tentacles  and 
footstalks.  On  the  second  day,  one  leaf  had  its 
blade  much  reflexed;  on  the  third  day  the  tentacles 
of  two  were  much  reflexed,  as  well  as  the  blades  of 
all  four  to  a greater  or  less  degree.  The  upper  side 
of  one  leaf,  instead  of  being,  as  at  first,  slightly 
concave,  now  presented  a strong  convexity  upwards. 
Even  on  the  fifth  day  the  leaves  did  not  appear  dead. 
Now,  as  sugar  does  not  in  the  least  excite  Drosera, 
we  may  safely  attribute  the  reflexion  of  the  blades 
and  tentacles  of  the  above  leaves  to  exosmose  from 
the  cells  which  were  in  contact  with  the  syrup,  and 
their  consequent  contraction.  When  drops  of  syrup 
are  placed  on  the  leaves  of  plants  with  their  roots  still 
in  damp  earth,  no  inflection  ensues,  for  the  roots,  no 
doubt,  pump  up  water  as  quickly  as  it  is  lost  by 
exosmose.  But  if  cut-off  leaves  are  immersed  in 
syrup,  or  in  any  dense  fluid,  the  tentacles  are  greatly, 
though  irregularly,  inflected,  some  of  them  assuming 
the  shape  of  corkscrews ; and  the  leaves  soon  become . 
flaccid.  If  they  are  now  immersed  in  a fluid  of  low 
specific  gravity,  the  tentacles  re-expand.  From  these 


Ohap.  X. 


SENSITIVENESS  OF  THE  LEAVES. 


233 


facts  we  may  conclude  that  drops  of  syrup  placed  on 
the  backs  of  leaves  do  not  act  by  exciting  a motor 
impulse  which  is  transmitted  to  the  tentacles ; but 
that  they  cause  reflexion  by  inducing  exosmose. 
Dr.  Nitschke  used  the  secretion  for  sticking  insects 
to  the  backs  of  the  leaves;  and  I suppose  that  he 
used  a large  quantity,  which  from  being  dense  pro- 
bably caused  exosmose.  Perhaps  he  experimented  on 
cut-off  leaves,  or  on  plants  with  their  roots  not  supplied 
with  enough  water. 

As  far,  therefore,  as  our  present  knowledge  serves, 
we  may  conclude  that  the  glands,  together  with  the 
immediately  underlying  cells  of  the  tentacles,  are 
the  exclusive  seats  of  that  irritability  or  sensitiveness 
with  which  the  leaves  are  endowed.  The  degree  to 
which  a gland  is  excited  can  be  measured  only  by 
the  number  of  the  surrounding  tentacles  which  are  in- 
flected, and  by  the  amount  and  rate  of  their  move- 
ment. Equally  vigorous  leaves,  exposed  to  the  same 
temperature  (and  this  is  an  important  condition), 
are  excited  in  different  degrees  under  the  following 
circumstances.  A minute  quantity  of  a weak  solu- 
tion produces  no  effect ; add  more,  or  give  a rather 
stronger  solution,  and  the  tentacles  bend.  Touch 
a gland  once  or  twice,  and  no  movement  follows; 
touch  it  three  or  four  times,  and  the  tentacle  becomes 
inflected.  But  the  nature  of  the  substance  which  is 
given  is  a very  important  element ; if  equal-sized  par- 
ticles of  glass  (which  acts  only  mechanically),  of 
gelatine,  and  raw  meat,  are  placed  on  the  discs  of 
several  leaves,  the  meat  causes  far  more  rapid,  ener- 
getic, and  widely  extended  movement  than  the  two 
former  substances.  The  number  of  glands  which  are 
excited  also  makes  a great  difference  in  the  result : 
place  a bit  of  meat  on  one  or  two  of  the  discaJ 


234 


DROSERA  ROTUNDIFOLIA. 


Chap.  X . 


glands,  and  only  a few  of  the  immediately  surround- 
ing short  tentacles  are  inflected ; place  it  on  several 
glands,  and  many  more  are  acted  on;  place  it  on 
thirty  or  forty,  and  all  the  tentacles,  including  the 
extreme  marginal  ones,  become  closely  inflected.  We 
thus  see  that  the  impulses  proceeding  from  a number 
of  glands  strengthen  one  another,  spread  farther,  and 
act  on  a larger  number*  of  tentacles,  than  the  im- 
pulse from  any  single  gland. 

Transmission  of  the  Motor  Impulse. — In  every  case 
the  impulse  from  a gland  has  to  travel  for  at  least 
a short  distance  to  the  basal  part  of  the  tentacle, 
the  upper  part  and  the  gland  itself  being  merely 
carried  by  the  inflection  of  the  lower  part.  The 
impulse  is  thus  always  transmitted  down  nearly 
the  whole  length  of  the  pedicel.  When  the  central 
glands  are  stimulated,  and  the  extreme  marginal  ten- 
tacles become  inflected,  the  impulse  is  transmitted 
across  half  the  diameter  of  the  disc;  and  when  the 
glands  on  one  side  of  the  disc  are  stimulated,  the 
impulse  is  transmitted  across  nearly  the  whole  width 
of  the  disc.  A gland  transmits  its  motor  impulse 
far  more  easily  and  quickly  down  its  own  tentacle 
to  the  bending  place  than  across  the  disc  to  neigh- 
bouring tentacles.  Thus  a minute  dose  of  a very 
weak  solution  of  ammonia,  if  given  to  one  of  the 
glands  of  the  exterior  tentacles,  causes  it  to  bend  and 
reach  the  centre;  whereas  a large  drop  of  the  same 
solution,  given  to  a score  of  glands  on  the  disc,  will 
not  cause  through  their  combined  influence  the  least 
inflection  of  the  exterior  tentacles.  Again,  when  a 
bit  of  meat  is  placed  on  the  gland  of  an  exterior 
tentacle,  I have  seen  movement  in  ten  seconds,  and 
repeatedly  within  a minute;  but  a much  larger  bit 
placed  on  several  glands  on  the  disc  does  not  cause 


Guap.  X.  TBANSMISSION  OF  MOTOR  IMPULSE. 


235 


the  exterior  tentacles  to  bend  until  half  an  hour  or 
even  several  hours  have  elapsed. 

The  motor  impulse  spreads  gradually  on  all  sides 
from  one  or  more  excited  glands,  so  that  the  ten- 
tacles which  stand  nearest  are  always  first  affected. 
Hence,  when  the  glands  in  the  centre  of  the  disc 
are  excited,  the  extreme  marginal  tentacles  are  the 
last  inflected.  But  the  glands  on  different  parts  of 
the  leaf  transmit  their  motor  power  in  a somewhat 
different  manner.  If  a bit  of  meat  be  placed  on 
the  long-headed  gland  of  a marginal  tentacle,  it 
quickly  transmits  an  impulse  to  its  own  bending 
portion ; but  never,  as  far  as  I have  observed,  to  the 
adjoining  tentacles;  for  these  are  not  affected  until 
the  meat  has  been  carried  to  the  central  glands, 
which  then  radiate  forth  their  conjoint  impulse  on  all 
sides.  On  four  occasions  leaves  were  prepared  by 
removing  some  days  previously  all  the  glands  from 
the  centre,  so  that  these  could  not  be  excited  by 
the  bits  of  meat  brought  to  them  by  the  inflection  of 
the  marginal  tentacles ; and  now  these  marginal  ten- 
tacles re-expanded  after  a time  without  any  other 
tentacle  being  affected.  Other  leaves  were  similarly 
prepared,  and  bits  of  meat  were  placed  on  the 
glands  of  two  tentacles  in  the  third  row  from  the  out- 
side, and  on  the  glands  of  two  tentacles  in  the  fifth 
row.  In  these  four  cases  the  impulse  was  sent 
in  the  first  place  laterally,  that  is,  in  the  same 
concentric  row  of  tentacles,  and  then  towards  the 
centre;  but  not  centrifugally,  or  towards  the  ex- 
terior tentacles.  In  one  of  these  cases  only  a single 
tentacle  on  each  side  of  the  one  with  meat  was 
affected.  In  the  three  other  cases,  from  half  a dozen 
to  a dozen  tentacles,  both  laterally  and  towards  the 
centre,  were  well  inflected  or  sub-inflected.  Lastly,  in 


236 


DROSEEA  ROTUNDIFOLIA. 


Chap.  X. 


ten  other  experiments,  minute  bits  of  meat  were  placed 
on  a single  gland  or  on  two  glands  in  the  centre  of  the 
disc.  In  order  that  no  other  glands  should  touch 
the  meat,  through  the  inflection  of  the  closely  adjoin- 
ing short  tentacles,  about  half  a dozen  glands  had 
been  previously  removed  round  the  selected  ones.  On 
eight  of  these  leaves  from  sixteen  to  twenty-five  of  the 
short  surrounding  tentacles  were  inflected  in  the  course 
of  one  or  two  days ; so  that  the  motor  impulse  radiat- 
ing from  one  or  two  of  the  discal  glands  is  able  to 
produce  this  much  effect.  The  tentacles  which  had 
been  removed  are  included  in  the  above  numbers  ; for, 
from  standing  so  close,  they  would  certainly  have  been 
affected.  On  the  two  remaining  leaves,  almost  all  the 
short  tentacles  on  the  disc  were  inflected.  With  a 
more  powerful  stimulus  than  meat,  namely  a little 
phosphate  of  lime  moistened  with  saliva,  I have  seen 
the  inflection  spread  still  farther  from  a single  gland 
thus  treated ; but  even  in  this  case  the  three  or  four 
outer  rows  of  tentacles  were  not  affected.  From  these 
experiments  it  appears  that  the  impulse  from  a single 
gland  on  the  disc  acts  on  a greater  number  of  ten- 
tacles than  that  from  a gland  of  one  of  the  exterior 
elongated  tentacles;  and  this  probably  follows,  at 
least  in  part,  from  the  impulse  having  to  travel  a very 
short  distance  down  the  pedicels  of  the  central  ten- 
tacles, so  that  it  is  able  to  spread  to  a considerable 
distance  all  round. 

Whilst  examining  these  leaves,  I was  struck  with  the 
fact  that  in  six,  perhaps  seven,  of  them  the  tentacles 
were  much  more  inflected  at  the  distal  and  proxi- 
mal ends  of  the  leaf  (i.  e.  towards  the  apex  and  base) 
than  on  either  side ; and  yet  the  tentacles  on  the  sides 
stood  as  near  to  the  gland  where  the  bit  of  meat  lay 
as  did  those  at  the  two  ends.  It  thus  appeared  as 


Chap.  X.  TKANSMISSION  OF  MOTOR  IMPULSE. 


237 


if  the  motor  impulse  was  transmitted  from  the  centre 
across  the  disc  more  readily  in  a longitudinal  than 
in  a transverse  direction ; and  as  this  appeared  a 
new  and  interesting  fact  in  the  physiology  of  plants, 
thirty-five  fresh  experiments  were  made  to  test  its 
truth.  Minute  bits  of  meat  were  placed  on  a single 
gland  or  on  a few  glands,  on  the  right  or  left  side  of 
the  discs  of  eighteen  leaves ; other  bits  of  the  same 
size  being  placed  on  the  distal  or  proximal  ends  of 
seventeen  other  leaves.  Now  if  the  motor  impulse 
were  transmitted  with  equal  force  or  at  an  equal  rate 
through  the  blade  in  all  directions,  a bit  of  meat 
placed  at  one  side  or  at  one  end  of  the  disc  ought  to 
affect  equally  all  the  tentacles  situated  at  an  equal 
distance  from  it;  but  this  certainly  is  not  the  case. 
Before  giving  the  general  results,  it  may  be  well  to 
describe  three  or  four  rather  unusual  cases. 


(1)  A minute  fragment  of  a fly  was  placed  on  one  side  of  the 
disc,  and  after  32  m.  seven  of  the  outer  tentacles  near  the  frag- 
ment were  inflected ; after  10  hrs.  several  more  became  so,  and 
after  23  hrs.  a still  greater  number ; and  now  the  blade  of  the 
leaf  on  this  side  was  bent  inwards  so  as  to  stand  up  at  right 
angles  to  the  other  side.  Neither  the  blade  of  the  leaf  nor  a 
single  tentacle  on  the  opposite  side  was  affected;  the  line  of 
separation  between  the  two  halves  extending  from  the  footstalk 
to  the  apex.  The  leaf  remained  in  this  state  for  three  days, 
and  on  the  fourth  day  began  to  re-expand;  not  a single  ten- 
tacle having  been  inflected  on  the  opposite  side. 

(2)  I will  here  give  a case  not  included  in  the  above  thirty- 
five  experiments.  A small  fly  was  found  adhering  by  its  feet  to 
the  left  side  of  the  disc.  The  tentacles  on  this  side  soon  closed 
in  and  killed  the  fly ; and  owing  probably  to  its  struggle  whilst 
alive,  the  leaf  was  so  much  excited  that  in  about  24  hrs.  all  the 
tentacles  on  the  opposite  side  became  inflected;  but  as  they 
found  no  prey,  for  their  glands  did  not  reach  the  fly,  they  re- 
expanded in  the  course  of  15  hrs. ; the  tentacles  on  the  left  side 
remaining  clasped  for  several  days. 

(3)  A bit  of  meat,  rather  larger  than  those  commonly  used. 


238 


DROSEKA  ROTUNDIFOLIA. 


Chap.  X. 


was  placed  in  a medial  line  at  the  basal  end  of  the  disc,  near 
the  footstalk;  after  2 hrs.  30  m.  some  neighbouring  tentacles 
were  inflected ; after  6 hrs.  the  tentacles  on  both  sides  of  the 
footstalk,  and  some  way  up  both  sides,  were  moderately  in- 
flected ; after  8 hrs.  the  tentacles  at  the  further  or  distal  end 
were  more  inflected  than  those  on  either  side;  after  23  hrs. 
the  meat  was  well  clasped  by  all  the  tentacles,  excepting  by  the 
exterior  ones  on  the  two  sides. 

(4)  Another  bit  of  meat  was  placed  at  the  opposite  or  distal 
end  of  another  leaf,  with  exactly  the  same  relative  results. 

(5)  A minute  bit  of  meat  was  placed  on  one  side  of  the  disc ; 
next  day  the  neighbouring  short  tentacles  were  inflected,  as 
well  as  in  a slight  degree  three  or  four  on  the  opposite  side 
near  the  footstalk.  On  the  second  day  these  latter  tentacles 
showed  signs  of  re-expanding,  so  I added  a fresh  bit  of  meat 
at  nearly  the  same  spot,  and  after  two  days  some  of  the  short 
tentacles  on  the  opposite  side  of  the  disc  were  inflected.  As 
soon  as  these  began  to  re-expand,  I added  another  bit  of  meat, 
and  next  day  all  the  tentacles  on  the  opposite  side  of  the  disc 
were  inflected  towards  the  meat;  whereas  we  have  seen  that 
those  on  the  same  side  were  affected  by  the  first  bit  of  meat 
which  was  given. 


Now  for  the  general  results.  Of  the  eighteen  leaves 
on  which  bits  of  meat  were  placed  on  the  right 
or  left  sides  of  the  disc,  eight  had  a vast  number  of 
tentacles  inflected  on  the  same  side,  and  in  four  of 
them  the  blade  itself  on  this  side  was  likewise  in- 
flected; whereas  not  a single  tentacle  nor  the  blade 
was  affected  on  the  opposite  side.  These  leaves  pre- 
sented a very  curious  appearance,  as  if  only  the  in- 
flected side  was  active,  and  the  other  paralysed.  In  the 
remaining  ten  cases,  a few  tentacles  became  inflected 
beyond  the  medial  line,  on  the  side  opposite  to  that 
where  the  meat  lay ; but,  in  some  of  these  cases,  only 
at  the  proximal  or  distal  ends  of  the  leaves.  The 
inflection  on  the  opposite  side  always  occurred  con- 
siderably after  that  on  the  same  side,  and  in  one  in- 
stance not  until  the  fourth  day.  We  have  also  seen 


Chap.  X.  TRANSMISSION  OF  MOTOR  IMPULSE. 


239 


with.  No.  5 that  bits  of  meat  had  to  be  added  thrice 
before  all  the  short  tentacles  on  the  opposite  side  of 
the  disc  were  inflected. 

The  result  was  widely  different  when  bits  of  meat 
were  placed  in  a medial  line  at  the  distal  or  proximal 
ends  of  the  disc.  In  three  of  the  seventeen  experi- 
ments thus  made,  owing  either  to  the  state  of  the  leaf 
or  to  the  smallness  of  the  bit  of  meat,  only  the  im- 
mediately adjoining  tentacles  were  affected ; but  in  the 
other  fourteen  cases  the  tentacles  at  the  opposite  end 
of  the  leaf  were  inflected,  though  these  were  as  distant 
from  where  the  meat  lay  as  were  those  on  one  side  of 
the  disc  from  the  meat  on  the  opposite  side.  In  some 
of  the  present  cases  the  tentacles  on  the  sides  were  not 
at  all  affected,  or  in  a less  degree,  or  after  a longer 
interval  of  time,  than  those  at  the  opposite  end.  One 
set  of  experiments  is  worth  giving  in  fuller  detail. 
Cubes  of  meat,  not  quite  so  small  as  those  usually  em- 
ployed, were  placed  on  one  side  of  the  discs  of  four 
leaves,  and  cubes  of  the  same  size  at  the  proximal 
or  distal  end  of  four  other  leaves.  Now,  when  these 
two  sets  of  leaves  were  compared  after  an  interval  of 
24  hrs.,  they  presented  a striking  difference.  Those 
having  the  cubes  on  one  side  were  very  slightly 
affected  on  the  opposite  side ; whereas  those  with  the 
cubes  at  either  end  had  almost  every  tentacle  at  the 
opposite  end,  even  the  marginal  ones,  closely  in- 
flected. After  48  hrs.  the  contrast  in  the  state  of  the 
two  sets  was  still  great ; yet  those  with  the  meat  on 
one  side  now  had  their  discal  and  submarginal  ten- 
tacles on  the  opposite  side  somewhat  inflected,  this 
being  due  to  the  large  size  of  the  cubes.  Finally  we 
may  conclude  from  these  thirty-five  experiments,  not 
to  mention  the  six  or  seven  previous  ones,  that  the 
motor  impulse  is  transmitted  from  any  single  gland 


240 


DROSERA  ROTUNDIFOLIA. 


Chap.  X 


or  small  group  of  glands  through  the  blade  to  the 
other  tentacles  more  readily  and  effectually  in  a 
longitudinal  than  in  a transverse  direction. 

As  long  as  the  glands  remain  excited,  and  this  may 
last  for  many  days,  even  for  eleven,  as  when  in  contact 
with  phosphate  of  lime,  they  continue  to  transmit  a 
motor  impulse  to  the  basal  and  bending  parts  of  their 
own  pedicels,  for  otherwise  they  would  re-expand.  The 
great  difference  in  the  length  of  time  during  which 
tentacles  remain  inflected  over  inorganic  objects,  and 
over  objects  of  the  same  size  containing  soluble  nitro- 
genous matter,  proves  the  same  fact.  But  the  intensity 
of  the  impulse  transmitted  from  an  excited  gland, 
which  has  begun  to  pour  forth  its  acid  secretion  and 
is  at  the  same  time  absorbing,  seems  to  be  very  small 
compared  with  that  which  it  transmits  when  first  ex- 
cited. Thus,  when  moderately  large  bits  of  meat  were 
placed  on  one  side  of  the  disc,  and  the  discal  and  sub- 
marginal tentacles  on  the  opposite  side  became  in- 
flected, so  that  their  glands  at  last  touched  the  meat 
and  absorbed  matter  from  it,  they  did  not  transmit 
any  motor  influence  to  the  exterior  rows  of  tentacles 
on  the  same  side,  for  these  never  became  inflected. 
If,  however,  meat  had  been  placed  on  the  glands  of 
these  same  tentacles  before  they  had  begun  to  secrete 
copiously  and  to  absorb,  they  undoubtedly  would  have 
affected  the  exterior  rows.  Nevertheless,  when  I gave 
some  phosphate  of  lime,  which  is  a most  powerful 
stimulant,  to  several  submarginal  tentacles  already 
considerably  inflected,  but  not  yet  in  contact  with 
some  phosphate  previously  placed  on  two  glands  in  the 
centre  of  the  disc,  the  exterior  tentacles  on  the  same 
side  were  acted  on. 

When  a gland  is  first  excited,  the  motor  impulse  is 
discharged  within  a few  seconds,  as  we  know  from  the  - 


Chap.  X.  TRANSMISSION  OF  MOTOR  IMPULSE. 


241 


bending  of  the  tentacle;  and  it  appears  to  be  dis- 
charged at  first  with  much  greater  force  than  after- 
wards. Thus,  in  the  case  above  given  of  a small  fly 
naturally  caught  by  a few  glands  on  one  side  of  a leaf, 
an  impulse  was  slowly  transmitted  from  them  across 
the  whole  breadth  of  the  leaf,  causing  the  opposite 
tentacles  to  be  temporarily  inflected,  but  the  glands 
which  remained  in  contact  with  the  insect,  though 
they  continued  for  several  days  to  send  an  impulse 
down  their  own  pedicels  to  the  bending  place,  did 
not  prevent  the  tentacles  on  the  opposite  side  from 
quickly  re-expanding ; so  that  the  motor  discharge 
must  at  first  have  been  more  powerful  than  afterwards. 

When  an  object  of  any  kind  is  placed  on  the  disc, 
and  the  surrounding  tentacles  are  inflected,  their 
glands  secrete  more  copiously  and  the  secretion 
becomes  acid,  so  that  some  influence  is  sent  to 
them  from  the  discal  glands.  This  change  in  the 
nature  and  amount  of  the  secretion  cannot  depend 
on  the  bending  of  the  tentacles,  as  the  glands  of  the 
short  central  tentacles  secrete  acid  when  an  object  is 
placed  on  them,  though  they  do  not  themselves  bend. 
Therefore  I inferred  that  the  glands  of  the  disc  sent 
some  influence  up  the  surrounding  tentacles  to  their 
glands,  and  that  these  reflected  back  a motor  impulse 
to  their  basal  parts ; but  this  view  was  soon  proved 
erroneous.  It  was  found  by  many  trials  that  tentacles 
with  their  glands  closely  cut  off  by  sharp  scissors 
often  become  inflected  and  again  re-expand,  still 
appearing  healthy.  One  which  was  observed  con- 
tinued healthy  for  ten  days  after  the  operation.  I 
therefore  cut  the  glands  off  twenty-five  tentacles, 
at  different  times  and  on  different  leaves,  and  seven- 
teen of  these  soon  became  inflected,  and  afterwards 
re-expanded.  The  re-expansion  commenced  in  about 


242 


DROSERA  ROTUNDIFOLIA. 


Chap.  X. 


8 hrs.  or  9 hrs.,  and  was  completed  in  from  22  hrs.  to 
30  hrs.  from  the  time  of  inflection.  After  an  interval 
of  a day  or  two,  raw  meat  with  saliva  was  placed  on  the 
discs  of  these  seventeen  leaves,  and  when  observed 
next  day,  seven  of  the  headless  tentacles  were  inflected 
over  the  meat  as  closely  as  the  nninjured  ones  on 
the  same  leaves;  and  an  eighth  headless  tentacle 
became  inflected  after  three  additional  days.  The 
meat  was  removed  from  one  of  these  leaves,  and  the 
surface  washed  with  a little  stream  of  water,  and  after 
three  days  the  headless  tentacle  re-expanded  for  the 
second  time.  These  tentacles  without  glands  were,  how- 
ever, in  a different  state  from  those  provided  with  glands 
and  which  had  absorbed  matter  from  the  meat,  for  the 
protoplasm  within  the  cells  of  the  former  had  under- 
gone far  less  aggregation.  From  these  experiments 
with  headless  tentacles  it  is  certain  that  the  glands 
do  not,  as  far  as  the  motor  impulse  is  concerned,  act  in 
a reflex  manner  like  the  nerve-ganglia  of  animals. 

But  there  is  another  action,  namely  that  of  aggrega- 
tion, which  in  certain  cases  may  be  called  reflex,  and 
it  is  the  only  known  instance  in  the  vegetable  king- 
dom. We  should  bear  in  mind  that  the  process  does 
not  depend  on  the  previous  bending  of  the  tentacles, 
as  we  clearly  see  when  leaves  are  immersed  in  certain 
strong  solutions.  Nor  does  it  depend  on  increased 
secretion  from  the  glands,  and  this  is  shown  by  several 
facts,  more  especially  by  the  papillae,  which  do  not 
secrete,  yet  undergoing  aggregation,  if  given  carbonate 
of  ammonia  or  an  infusion  of  raw  meat.  When  a gland 
is  directly  stimulated  in  any  way,  as  by  the  pressure  of 
a minute  particle  of  glass,  the  protoplasm  within  the 
cells  of  the  gland  first  becomes  aggregated,  then  that 
in  the  cells  immediately  beneath  the  gland,  and  so 
lower  and  lower  dowm  the  tentacles  to  their  bases ; — 


Chap.  X.  DIKECTION  OF  INFLECTED  TENTACLES.  243 


that  is,  if  the  stimulus  has  been  sufficient  and  not 
injurious.  Now,  when  the  glands  of  the  disc  are 
excited,  the  exterior  tentacles  are  affected  in  exactly 
the  same  manner:  the  aggregation  always  com- 
mences in  their  glands,  though  these  have  not  been 
directly  excited,  but  have  only  received  some  influ- 
ence from  the  disc,  as  shown  by  their  increased  acid 
secretion.  The  protoplasm  within  the  cells  immedi- 
ately beneath  the  glands  are  next  affected,  and  so 
downwards  from  cell  to  cell  to  the  bases  of  the 
tentacles.  This  process  apparently  deserves  to  be 
called  a reflex  action,  in  the  same  manner  as  when  a 
sensory  nerve  is  irritated,  and  carries  an  impression 
to  a ganglion  which  sends  back  some  influence  to  a 
muscle  or  gland,  causing  movement  or  increased 
secretion ; but  the  action  in  the  two  cases  is  probably 
of  a widely  different  nature.  After  the  protoplasm  in  a 
tentacle  has  been  aggregated,  its  redissolution  always 
begins  in  the  lower  part,  and  slowly  travels  up  the 
pedicel  to  the  gland,  so  that  the  protoplasm  last 
aggregated  is  first  redissolved.  This  probably  depends 
merely  on  the  protoplasm  being  less  and  less  aggre- 
gated, lower  and  lower  down  in  the  tentacles,  as  can 
be  seen  plainly  when  the  excitement  has  been  slight. 
As  soon,  therefore,  as  the  aggregating  action  altogether 
ceases,  redissolution  naturally  commences  in  the  less 
strongly  aggregated  matter  in  the  lowest  part  of  the 
tentacle,  and  is  there  first  completed. 

Direction  of  the  Inflected  Tentacles. — When  a particle 
of  any  kind  is  placed  on  the  gland  of  one  of  the  outer 
tentacles,  this  invariably  moves  towards  the  centre  of 
the  leaf ; and  so  it  is  with  all  the  tentacles  of  a leaf 
immersed  in  any  exciting  fluid.  The  glands  of  the 
exterior  tentacles  then  form  a ring  round  the  middle 
part  of  the  disc,  as  shown  in  a previous  figure  (fig.  4. 


244 


DROSEKA  ROTUNDIFOLIA. 


Chap.  X. 


p.  10).  The  short  tentacles  within  this  ring  still 
retain  their  vertical  position,  as  they  likewise  do  when 
a large  object  is  placed  on  their  glands,  or  when  an 
insect  is  caught  by  them.  In  this  latter  case  we  can 
see  that  the  inflection  of  the  short  central  tentacles 
would  be  useless,  as  their  glands  are  already  in  con- 
tact with  their  prey. 

The  result  is  very  different  when  a single  gland  on 
one  side  of  the  disc  is  excited,  or  a few  in  a group, 

These  send  an  impulse  to 
the  surrounding  tentacles, 
which  do  not  now  bend 
towards  the  centre  of  the 
leaf,  but  to  the  point 
of  excitement.  We  owe 
this  capital  observation  to 
Nitschke,^  and  since  read- 
ing his  paper  a few  years 
ago,  I have  repeatedly 
verified  it.  If  a minute  bit 
of  meat  be  placed  by  the 
aid  of  a needle  on  a single 
gland,  or  on  three  or  four 
together,  halfway  between 
the  centre  and  the  circum- 
, , s ference  of  the  disc,  the 

(^Drosera  rotundifolia.)  , ^ 

Leaf  (enlarged)  with  the  tentacles  inflected  directed  mOVCmCnt  of  the 

?hTdL^.“  surrounding  tentacles  is 

well  exhibited.  An  accu- 
rate drawing  of  a leaf  with  meat  in  this  position  is 
here  reproduced  (fig.  10),  and  we  see  the  tentacles,  in- 
cluding some  of  the  exterior  ones,  accurately  directed 
to  the  point  where  the  meat  lay.  But  a much  better 


Fig.  10. 


♦ ‘Bot.  Zeitung,*  18G0,  p.  240. 


Chap.  X.  DIRECTION  OF  INFLECTED  TENTACLES.  245 


plan  is  to  place  a particle  of  the  phosphate  of  lime 
moistened  with  saliva  on  a single  gland  on  one  side 
of  the  disc  of  a large  leaf,  and  another  particle  on  a 
single  gland  on  the  opposite  side.  In  four  such 
trials  the  excitement  was  not  sufficient  to  affect  the 
outer  tentacles,  but  all  those  near  the  two  points 
were  directed  to  them,  so  that  two  wheels  were  formed 
on  the  disc  of  the  same  leaf ; the  pedicels  of  the 
tentacles  forming  the  spokes,  and  the  glands  united 
in  a mass  over  the  phosphate  representing  the  axles. 
The  precision  with  which  each  tentacle  pointed  to 
the  particle  was  wonderful ; so  that  in  some  cases  I 
could  detect  no  deviation  from  perfect  accuracy. 
Thus,  although  the  short  tentacles  in  the  middle  of 
the  disc  do  not  bend  when  their  glands  are  excited 
in  a direct  manner,  yet  if  they  receive  a motor  impulse 
from  a point  on  one  side,  they  direct  themselves  to  the 
point  equally  well  with  the  tentacles  on  the  borders  of 
the  disc. 

In  these  experiments,  some  of  the  short  tentacles  on 
the  disc,  which  would  have  been  directed  to  the  centre, 
had  the  leaf  been  immersed  in  an  exciting  fluid,  were 
now  inflected  in  an  exactly  opposite  direction,  viz. 
towards  the  circumference.  These  tentacles,  therefore, 
had  deviated  as  much  as  180°  from  the  direction  which 
they  would  have  assumed  if  their  own  glands  had 
been  stimulated,  and  which  may  be  considered  as  the 
normal  one.  Between  this,  the  greatest  possible  and  no 
deviation  from  the  normal  direction,  every  degree  could 
be  observed  in  the  tentacles  on  these  several  leaves. 
Notwithstanding  the  precision  with  which  the  tentacles 
generally  were  directed,  those  near  the  circumference 
of  one  leaf  were  not  accurately  directed  towards  some 
phosphate  of  lime  at  a rather  distant  point  on  the 
opposite  side  of  the  disc.  It  appeared  as  if  the  motoi 


246 


DROSERA  ROTUNDIFOLIA. 


Chap.  X 


impulse  in  passing  transversely  across  nearly  the 
whole  width  of  the  disc  had  departed  somewhat  from 
a true  course.  This  accords  with  what  we  have 
already  seen  of  the  impulse  travelling  less  readily  in 
a transverse  than  in  a longitudinal  direction.  In 
some  other  cases,  the  exterior  tentacles  did  not  seem 
capable  of  such  accurate  movement  as  the  shorter 
and  more  central  ones. 

Nothing  could  be  more  striking  than  the  appear- 
ance of  the  above  four  leaves,  each  with  their  ten- 
tacles pointing  truly  to  the  two  little  masses  of  the 
phosphate  on  their  discs.  We  might  imagine  that  we 
were  looking  at  a lowly  organised  animal  seizing  prey 
with  its  arms.  In  the  case  of  Drosera  the  explanation 
of  this  accurate  power  of  movement,  no  doubt,  lies  in 
the  motor  impulse  radiating  in  all  directions,  and 
whichever  side  of  a tentacle  it  first  strikes,  that  side 
contracts,  and  the  tentacle  consequently  bends  towards 
the  point  of  excitement.  The  pedicels  of  the  tentacles 
are  flattened,  or  elliptic  in  section.  Near  the  bases  of 
the  short  central  tentacles,  the  flattened  or  broad  face 
is  formed  of  about  five  longitudinal  rows  of  cells ; in 
the  outer  tentacles  of  the  disc  it  consists  of  about  six 
or  seven  rows ; and  in  the  extreme  marginal  tentacles 
of  above  a dozen  rows.  As  the  flattened  bases  are 
thus  formed  of  only  a few  rows  of  cells,  the  precision 
of  the  movements  of  the  tentacles  is  the  more  remark- 
able ; for  when  the  motor  impulse  strikes  the  base  of 
a tentacle  in  a very  oblique  direction  relatively  to  its 
broad  face,  scarcely  more  than  one  or  two  cells  towards 
one  end  can  be  affected  at  first,  and  the  contraction 
of  these  cells  must  draw  the  whole  tentacle  into  the 
proper  direction.  It  is,  perhaps,  owing  to  the  exterior 
pedicels  being  much  flattened  that  they  do  not  bend 
quite  so  accurately  to  the  point  of  excitement  as  the 


Chap.  X. 


CONDUCTING  TISSUES. 


247 


more  central  ones.  The  properly  directed  movement 
of  the  tentacles  is  not  an  unique  case  in  the  vegetable 
kingdom,  for  the  tendrils  of  many  plants  curve  to- 
wards the  side  which  is  touched ; but  the  case  of 
Drosera  is  far  more  interesting,  as  here  the  tentacles 
are  not  directly  excited,  but  receive  an  impulse  from 
a distant  point;  nevertheless,  they  bend  accurately 
towards  this  point. 

On  the  Nature  of  the  Tissues  through  which  the  Motor 
Impulse  is  Transmitted. — It  will  be  necessary  first 
to  describe  briefly  the 
course  of  the  main  fibro- 
vascular  bundles.  These 
are  shown  in  the  accom- 
panying sketch  (fig.  11) 
of  a small  leaf.  Little 
vessels  from  the  neigh- 
bouring bundles  enter 
all»  the  many  tentacles 
with  which  the  surface 
is  studded ; but  these 
are  not  liere  represented. 

The  central  trunk,  which 
runs  up  the  footstalk, 
bifurcates  near  the  centre 
of  the  leaf,  each  branch 
bifurcating  again  and 
again  according  to  the 
size  of  the  leaf.  This 
central  trunk  sends  off,  low  down  on  each  side,  a 
delicate  branch,  which  may  be  called  the  sublateral 
branch.  There  is  also,  on  each  side,  a main  lateral 
branch  or  bundle,  which  bifurcates  in  the  same 
manner  as  the  others.  Bifurcation  does  not  imply 
that  any  single  vessel  divides,  but  that  a bundle 


Fig.  11. 

(Drotera  rotundifolia.') 
Diagram  showing  the  distribution  of  the 
vascular  tissue  in  a small  leaf. 


248  ^ DROSERA  ROTUNDIFOLIA.  CiiAP.  X. 

divides  into  two.  By  looking  to  either  side  of  the 
leaf,  it  will  be  seen  that  a branch  from  the  great 
central  bifurcation  inosculates  with  a branch  from  the 
lateral  bundle,  and  that  there  is  a smaller  inoscu- 
lation between  the  two  chief  branches  of  the  lateral 
bundle.  The  course  of  the  vessels  is  very  complex 
at  the  larger  inosculation ; and  here  vessels,  retain- 
ing the  same  diameter,  are  often  formed  by  the 
union  of  the  bluntly  pointed  ends  of  two  vessels, 
but  whether  these  points  open  into  each  other  by 
their  attached  surfaces,  I do  not  know.  By  means 
of  the  two  inosculations  all  the  vessels  on  the 
same  side  of  the  leaf  are  brought  into  some  sort  of 
connection.  Near  the  circumference  of  the  larger 
leaves  the  bifurcating  branches  also  come  into  close 
union,  and  then  separate  again,  forming  a continuous 
zigzag  line  of  vessels  round  the  whole  circumference. 
But  the  union  of  the  vessels  in  this  zigzag  line  seems 
to  be  much  less  intimate  than  at  the  main  inoscula- 
tion. It  should  be  added  that  the  course  of  the 
vessels  differs  somewhat  in  different  leaves,  and  even 
on  opposite  sides  of  the  same  leaf,  but  the  main 
inosculation  is  always  present. 

Now  iu  my  first  experiments  with  bits  of  meat 
placed  on  one  side  of  the  disc,  it  so  happened  that  not 
a single  tentacle  was  inflected  on  the  opposite  side ; 
and  when  I saw  that  the  vessels  on  the  same  side  were 
all  connected  together  by  the  two  inosculations,  whilst 
not  a vessel  passed  over  to  the  opposite  side,  it  seemed 
probable  that  the  motor  impulse  wns  conducted  ex- 
clusively along  them. 

In  order  to  test  this  view,  I divided  transversely 
with  the  point  of  a lancet  the  central  trunks  of  four 
leaves,  just  beneath  the  main  bifurcation;  and  two 
days  afterwards  placed  rather  large  bits  of  raw  meat 


OlIAP.  X. 


CONDUCTING  TISSUES. 


249 


(a  most  powerful  stimulant)  near  the  centre  of  the 
disc  above  the  incision — that  is,  a little  towards  the 
apex — with  the  following  results  : — 

(1)  This  leaf  proved  rather  torpid : after  4 hrs.  40  m.  (in  all 
cases  reckoning  from  the  time  when  the  meat  was  given)  the 
tentacles  at  the  distal  end  were  a little  inflected,  but  nowhere 
else ; they  remained  so  for  three  days,  and  re-expanded  on  the 
fourth  day.  The  leaf  was  then  dissected,  and  the  trunk,  as  well 
as  the  two  sublateral  branches,  were  found  divided. 

(2)  After  4 hrs.  30  m.  many  of  the  tentacles  at  the  distal  end 
were  well  inflected.  Next  day  the  blade  and  all  the  tentacles  at 
this  end  were  strongly  inflected,  and  were  separated  by  a dis- 
tinct transverse  line  from  the  basal  half  of  the  leaf,  which  was 
not  in  the  least  affected.  On  the  third  day,  however,  some  of 
the  short  tentacles  on  the  disc  near  the  base  were  very  slightly 
inflected.  The  incision  was  found  on  dissection  to  extend  across 
the  leaf  as  in  the  last  case. 

(3)  After  4 hrs.  30  m.  strong  inflection  of  the  tentacles  at 
the  distal  end,  which  during  the  next  two  days  never  extended 
in  the  least  to  the  basal  end.  The  incision  as  before. 

(4)  This  leaf  was  not  observed  until  15  hrs.  had  elapsed,  and 
then  all  the  tentacles,  except  the  extreme  marginal  ones,  were 
found  equally  well  inflected  all  round  the  leaf.  On  careful 
examination  the  spiral  vessels  of  the  central  trunk  were  cer- 
tainly divided;  but  the  incision  on  one  side  had  not  passed 
through  the  fibrous  tissue  surrounding  these  vessels,  though  it 
had  passed  through  the  tissue  on  the  other  side.* 

The  appearance  presented  by  the  leaves  (2)  and  (3) 
was  very  curious,  and  might  be  aptly  compared  with 
that  of  a man  with  his  backbone  broken  and  lower  ex- 
tremities paralysed.  Excepting  that  the  line  between 
the  two  halves  was  here  transverse  instead  of  longitu- 
dinal, these  leaves  were  in  the  same  state  as  some  of 
those  in  the  former  experiments,  with  bits  of  meat 
placed  on  one  side  of  the  disc.  The  case  of  leaf  (4) 


* M.  Ziegler  made  similar  ex-  ^/Comptes  rendus,’  1874,  p.  1417), 
periments  by  cutting  the  spiral  but  arrived  at  conclusions  widely 
vessels  of  Drosem  intermedia  different  from  mine. 


250 


DROSERA  ROTUNDIFOLIA. 


Chap.  X. 


proves  that  the  spiral  vessels  of  the  central  trunk  may 
be  divided,  and  yet  the  motor  impulse  be  transmitted 
from  the  distal  to  the  basal  end ; and  this  led  me  at 
first  to  suppose  that  the  motor  force  was  sent  through 
the  closely  surrounding  fibrous  tissue ; and  that  if  one 
half  of  this  tissue  was  left  undivided,  it  sufficed  for 
complete  transmission.  But  opposed  to  this  conclusion 
is  the  fact  that  no  vessels  pass  directly  from  one  side 
of  the  leaf  to  the  other,  and  yet,  as  we  have  seen,  if 
a rather  large  bit  of  meat  is  placed  on  one  side,  the 
motor  impulse  is  sent,  though  slowly  and  imperfectly, 
in  a transverse  direction  across  the  whole  breadth  of 
the  leaf.  Nor  can  this  latter  fact  be  accounted  for 
by  supposing  that  the  transmission  is  effected  through 
the  two  inosculations,  or  through  the  circumferential 
zigzag  line  of  union,  for  had  this  been  the  case,  the 
exterior  tentacles  on  the  opposite  side  of  the  disc 
would  have  been  affected  before  the  more  central  ones, 
which  never  occurred.  We  have  also  seen  that  the 
extreme  marginal  tentacles  appear  to  have  no  power 
to  transmit  an  impulse  to  the  adjoining  tentacles ; yet 
the  little  bundle  of  vessels  which  enters  each  marginal 
tentacle  sends  off  a minute  branch  to  those  on  both 
sides,  and  this  I have  not  observed  in  any  other  ten- 
tacles; so  that  the  marginal  ones  are  more  closely 
connected  together  by  spiral  vessels  than  are  the 
others,  and  yet  have  much  less  power  of  communi- 
cating a motor  impulse  to  one  another. 

But  besides  these  several  facts  and  arguments  we 
have  conclusive  evidence  that  the  motor  impulse  is 
not  sent,  at  least  exclusively,  through  the  spiral 
vessels,  or  through  the  tissue  immediately  surrounding 
them.  We  know  that  if  a bit  of  meat  is  placed  on  a 
gland  (the  immediately  adjoining  ones  having  been 
removed)  on  any  part  of  the  disc,  all  the  short  sur- 


Chap.  X. 


CONDUCTING  TISSUES. 


251 


rounding  tentacles  bend  almost  simultaneously  with 
great  precision  towards  it.  Now  there  are  tentacles 
on  the  disc,  for  instance  near  the  extremities  of  the 
sublateral  bundles  (fig.  11),  which  are  supplied  with 
vessels  that  do  not  come  into  contact  with  the  branches 
that  enter  the  surrounding  tentacles,  except  by  a very 
long  and  extremely  circuitous  course.  Nevertheless, 
if  a bit  of  meat  is  placed  on  the  gland  of  a tentacle 
of  this  kind,  all  the  surrounding  ones  are  inflected 
towards  it  with  great  precision.  It  is,  of  course,  pos- 
sible that  an  impulse  might  be  sent  through  a long 
and  circuitous  course,  but  it  is  obviously  impossible 
that  the  direction  of  the  movement  could  be  thus 
communicated,  so  that  all  the  surrounding  tentacles 
should  bend  precisely  to  the  point  of  excitement.  The 
impulse  no  doubt  is  transmitted  in  straight  radiating 
lines  from  the  excited  gland  to  the  surrounding  ten- 
tacles; it  cannot,  therefore,  be  sent  along  the  fibro- 
vascular  bundles.  The  effect  of  cutting  the  central 
vessels,  in  the  above  cases,  in  preventing  the  transmis- 
sion of  the  motor  impulse  from  the  distal  to  the  basal 
end  of  a leaf,  may  be  attributed  to  a considerable  space 
of  the  cellular  tissue  having  been  divided.  We  shall 
hereafter  see,  when  we  treat  of  Dionaea,  that  this  same 
conclusion,  namely  that  the  motor  impulse  is  not 
transmitted  by  the  fibro-vascular  bundles,  is  plainly 
confirmed ; and  Professor  Cohn  has  come  to  the  same 
conclusion  with  respect  to  Aldrovanda — both  members 
of  the  Droserace80. 

As  the  motor  impulse  is  not  transmitted  along  the 
vessels,  there  remains  for  its  passage  only  the  cellular 
tissue ; and  the  structure  of  this  tissue  explains  to  a 
certain  extent  how  it  travels  so  quickly  down  the  long 
exterior  tentacles,  and  much  more  slowly  across  the 
blade  of  the  leaf.  We  shall  also  see  why  it  crosses 


252 


DROSERA  ROTUNDIFOLIA. 


Chap.  X. 


the  blade  more  quickly  in  a longitudinal  than  in  a 
transverse  direction ; though  with  time  it  can  pass  in 
any  direction.  We  know  that  the  same  stimulus 
causes  movement  of  the  tentacles  and  aggregation  of 
the  protoplasm,  and  that  both  influences  originate  in 
and  proceed  from  the  glands  within  the  same  brief 
space  of  time.  It  seems  therefore  probable  that  the 
motor  impulse  consists  of  the  first  commencement  of 
a molecular  change  in  the  protoplasm,  which,  when 
well  developed,  is  plainly  visible,  and  has  been  desig- 
nated aggregation ; but  to  this  subject  I shall  return. 
We  further  know  that  in  the  transmission  of  the  aggre- 
gating process  the  chief  delay  is  caused  by  the  passage 
of  the  transverse  cell- walls;  for  as  the  aggregation 
travels  down  the  tentacles,  the  contents  of  each  suc- 
cessive cell  seem  almost  to  flash  into  a cloudy  mass. 
We  may  therefore  infer  that  the  motor  impulse  is  in 
like  manner  delayed  chiefly  by  passing  through  the 
cell-walls. 

The  greater  celerity  with  which  the  impulse  is 
transmitted  down  the  long  exterior  tentacles  than 
across  the  disc  may  be  largely  attributed  to  its  being 
closely  confined  within  the  narrow  pedicel,  instead 
of  radiating  forth  on  all  sides  as  on  the  disc.  But 
besides  this  confinement,  the  exterior  cells  of  the  ten- 
tacles are  fully  twice  as  long  as  those  of  the  disc ; so 
that  only  half  the  number  of  transverse  partitions 
/ have  to  be  traversed  in  a given  length  of  a tentacle, 
compared  with  an  equal  space  on  the  disc ; and  there 
would  be  in  the  same  proportion  less  retardation  of  the 
impulse.  Moreover,  in  sections  of  the  exterior  ten- 
tacles given  by  Dr.  Warming,*  the  parenchymatous 


* ‘ Yidenskabelige  Meddelolser  de  la  Soc.  d’Hlst.  nat.  de  Copen 
hague,'  Nos.  10-12,  1872,  woodcuts  iv.  and  v. 


Chap.  X. 


CONDUCTING  TISSUES. 


253 


cells  are  shown  to  be  still  more  elongated ; and  these 
would  form  the  most  direct  line  of  communication  from 
the  gland  to  the  bending  place  of  the  tentacle.  If  the 
impulse  travels  down  the  exterior  cells,  it  would  have 
to  cross  from  between  twenty  to  thirty  transverse  par- 
titions ; but  rather  fewer  if  down  the  inner  parenchy- 
matous tissue.  In  either  case  it  is  remarkable  that 
the  impulse  is  able  to  pass  through  so  many  par- 
titions down  nearly  the  whole  length  of  the  pedicel, 
and  to  act  on  the  bending  place,  in  ten  seconds.  Why 
the  impulse,  after  having  passed  so  quickly  down  one 
of  the  extreme  marginal  tentacles  (about  of  an 
inch  in  length),  should  never,  as  far  as  I have  seen, 
affect  the  adjoining  tentacles,  I do  not  understand. 
It  may  be  in  part  accounted  for  by  much  energy 
being  expended  in  the  rapidity  of  the  transmission. 

Most  of  the  cells  of  the  disc,  both  the  superficial 
ones  and  the  larger  cells  which  form  the  five  or  six 
underlying  layers,  are  about  four  times  as  long  as 
broad.  They  are  arranged  almost  longitudinally, 
radiating  from  the  footstalk.  The  motor  impulse, 
therefore,  when  transmitted  across  the  disc,  has  to 
cross  nearly  four  times  as  many  cell-walls  as  when 
transmitted  in  a longitudinal  direction,  and  would 
consequently  be  much  delayed  in  the  former  case. 
The  cells  of  the  disc  converge  towards  the  bases  of 
the  tentacles,  and  are  thus  fitted  to  convey  the  motor 
impulse  to  them  from  all  sides.  On  the  whole,  the 
arrangement  and  shape  of  the  cells,  both  those  of  the 
disc  and  tentacles,  throw  much  light  on  the  rate  and 
manner  of  diffusion  of  the  motor  impulse.  But  why 
the  impulse  proceeding  from  the  glands  of  the  ex- 
terior rows  of  tentacles  tends  to  travel  laterally  and 
towards  the  centre  of  the  leaf,  but  not  centrifugally,  is 
by  no  means  clear. 


254  DKOSERA  ROTUNDIFOLIA.  Chap.  X. 

Mechanism  of  the  Movements,  and  Nature  of  the 
Motor  Impulse, — Whatever  may  be  the  means  of 
movement,  the  exterior  tentacles,  considering  their 
delicacy,  are  inflected  with  much  force.  A bristle, 
held  so  that  a length  of  1 inch  projected  from  a 
handle,  yielded  when  I tried  to  lift  with  it  an  in- 
flected tentacle,  which  was  somewhat  thinner  than  the 
bristle.  The  amount  or  extent,  also,  of  the  movement 
is  great.  Fully  expanded  tentacles  in  becoming  in- 
flected sweep  through  an  angle  of  180°;  and  if  they 
are  beforehand  reflexed,  as  often  occurs,  the  angle  is 
considerably  greater.  It  is  probably  the  superficial 
cells  at  the  bending  place  which  chiefly  or  exclusively 
contract;  for  the  interior  cells  have  very  delicate 
walls,  and  are  so  few  in  number  that  they  could  hardly 
cause  a tentacle  to  bend  with  precision  to  a definite 
point.  Though  I carefully  looked,  I could  never 
detect  any  wrinkling  of  the  surface  at  the  bending 
place,  even  in  the  case  of  a tentacle  abnormally 
curved  into  a complete  circle,  under  circumstances 
hereafter  to  be  mentioned. 

All  the  cells  are  not  acted  on,  though  the  motor 
impulse  passes  through  them.  When  the  gland  of 
one  of  the  long  exterior  tentacles  is  excited,  the 
upper  cells  are  not  in  the  least  affected ; about  half- 
way down  there  is  a slight  bending,  but  the  chief 
movement  is  confined  to  a short  space  near  the  base; 
and  no  part  of  the  inner  tentacles  bends  except  the 
basal  portion.  With  respect  to  the  blade  of  the  leaf, 
the  motor  impulse  may  be  transmitted  through  many 
cells,  from  the  centre  to  the  circumference,  without 
their  being  in  the  least  affected,  or  they  may  be 
strongly  acted  on  and  the  blade  greatly  inflected. 
In  the  latter  case  the  movement  seems  to  depend 
partly  on  the  strength  of  the  stimulus,  and  partly  on 


Chap.  X. 


MEANS  OF  MOVEMENT. 


255 


its  nature,  as  when  leaves  are  immersed  in  certain 
fluids. 

The  power  of  movement  which  various  plants  possess, 
when  irritated,  has  been  attributed  by  high  authorities 
to  the  rapid  passage  of  fluid  out  of  certain  cells,  which, 
from  their  previous  state  of  tension,  immediately  con- 
tract.* Whether  or  not  this  is  the  primary  cause  of 
such  movements,  fluid  must  pass  out  of  closed  cells 
when  they  contract  or  are  pressed  together  in  one 
direction,  unless  they  at  the  same  time  expand  in 
some  other  direction.  For  instance,  fluid  can  be  seen 
to  ooze  from  the  surface  of  any  young  and  vigorous 
shoot  if  slowly  bent  into  a semi-circle.t  In  the  case 
of  Drosera  there  is  certainly  much  movement  of  the 
fluid  throughout  the  tentacles  whilst  they  are  under- 
going inflection.  Many  leaves  can  be  found  in  which 
the  purple  fluid  within  the  cells  is  of  an  equally  dark 
tint  on  the  upper  and  lower  sides  of  the  tentacles, 
extending  also  downwards  on  both  sides  to  equally 
near  their  bases.  If  the  tentacles  of  such  a leaf  are 
excited  into  movement,  it  will  generally  be  found  after 
some  hours  that  the  cells  on  the  concave  side  are  much 
paler  than  they  were  before,  or  are  quite  colourless, 
those  on  the  convex  side  having  become  much  darker. 
In  two  instances,  after  particles  of  hair  had  been  placed 
on  glands,  and  when  in  the  course  of  1 hr.  10  m.  the 
tentacles  were  incurved  halfway  towards  the  centre 
of  the  leaf,  this  change  of  colour  in  the  two  sides  was 
conspicuously  plain.  In  another  case,  after  a bit  of 
meat  had  been  placed  on  a gland,  the  purple  colour 
was  observed  at  intervals  to  be  slowly  travelling  from 
the  upper  to  the  lower  part,  down  the  convex  side  of 


* Sachs,  ‘Traite  de  Bot.*  3rd  Lamarck, 
edit.  1874,  p.  1038.  This  view  f Sachs,  ibid.  p.  919. 
was,  I believe,  first  suggested  by 

12 


256 


DKOSEKA  KOTUNDI  FOLIA. 


Ohap.  X. 


the  bending  tentacle.  But  it  does  not  follow  from 
these  observations  that  the  cells  on  the  convex  side 
become  filled  with  more  fluid  during  the  act  of  in- 
flection than  they  contained  before ; for  fluid  may  all 
the  time  be  passing  into  the  disc  or  into  the  glands 
which  then  secrete  freely. 

The  bending  of  the  tentacles,  when  leaves  are  im- 
mersed in  a dense  fluid,  and  their  subsequent  re- 
expansion in  a less  dense  fluid,  show  that  the  passage 
of  fluid  from  or  into  the  celJs  can  cause  movements 
like  the  natural  ones.  But  the  inflection  thus  caused 
is  often  irregular ; the  exterior  tentacles  being  some- 
times spirally  curved.  Other  unnatural  movements 
are  likewise  caused  by  the  application  of  dense  fluids, 
as  in  the  case  of  drops  of  syrup  placed  on  the  backs 
of  leaves  and  tentacles.  Such  movements  may  be 
compared  with  the  contortions  which  many  vegetable 
tissues  undergo  when  subjected  to  exosmose.  It  is 
therefore  doubtful  whether  they  throw  any  light  on 
the  natural  movements. 

If  we  admit  that  the  outward  passage  of  fluid  is 
the  cause  of  the  bending  of  the  tentacles,  we  must 
suppose  that  the  cells,  before  the  act  of  inflection, 
are  in  a high  state  of  tension,  and  that  they  are 
elastic  to  an  extraordinary  degree ; for  otherwise  their 
contraction  could  not  cause  the  tentacles  often  to 
sweep  through  an  angle  of  above  180°.  Professor 
Cohn,  in  his  interesting  paper*  on  the  movements 
of  the  stamens  of  certain  Compositae,  states  that  these 
organs,  when  dead,  are  as  elastic  as  threads  of  india- 
rubber,  and  are  then  only  half  as  long  as  they  were 
when  alive.  He  believes  that  the  living  protoplasm 


♦ ‘ Abhand.  der  Schles.  Gesell.  is  given  in  the  ^ Annals  and  Mag. 
fiir  vaterl.  Cultur,  1861,  Heft  i.  of  Nat.  Hist.*  3rd  series,  1863, 
An  excellent  abstract  of  this  paper  vol.  xi.  pp.  188-197. 


CllAI  . X. 


MEANS  OF  MOVEMENT. 


257 


within  their  cells  is  ordinarily  in  a state  of  expansion, 
but  is  paralysed  by  irritation,  or  may  be  said  to  suffer 
temporary  death ; the  elasticity  of  the  cell-walls  then 
coming  into  play,  and  causing  the  contraction  of  the 
stamens.  Now  the  cells  on  the  upper  or  concave  side 
of  the  bending  part  of  the  tentacles  of  Drosera  do  not 
appear  to  be  in  a state  of  tension,  nor  to  be  highly 
elastic;  for  when  a leaf  is  suddenly  killed,  or  dies 
slowly,  it  is  not  the  upper  but  the  lower  sides  of  the 
tentacles  which  contract  from  elasticity.  We  may, 
therefore,  conclude  that  their  movements  cannot  be 
accounted  for  by  the  inherent  elasticity  of  certain 
cells,  opposed  as  long  as  they  are  alive  and  not  irri- 
tated by  the  expanded  state  of  their  contents. 

A somewhat  different  view  has  been  advanced  by 
other  physiologists  — namely  that  the  protoplasm, 
when  irritated,  contracts  like  the  soft  sarcode  of 
the  muscles  of  animals.  In  Drosera  the  fluid  within 
the  cells  of  the  tentacles  at  the  bending  place  appears 
under  the  microscope  thin  and  homogeneous,  and  after 
aggregation  consists  of  small,  soft  masses  of  matter, 
undergoing  incessant  changes  of  form  and  floating  in 
almost  colourless  fluid.  These  masses  are  completely 
redissolved  when  the  tentacles  re-expand.  Now  it 
seems  scarcely  possible  that  such  matter  should  have 
any  direct  mechanical  power;  but  if  through  some 
molecular  change  it  were  to  occupy  less  space  than  it 
did  before,  no  doubt  the  cell-walls  would  close  up  and 
contract.  But  in  this  case  it  might  be  expected  that 
the  walls  would  exhibit  wrinkles,  and  none  could  ever 
be  seen.  Moreover,  the  contents  of  all  the  cells  seem 
to  be  of  exactly  the  same  nature,  both  before  and  after 
aggregation;  and  yet  only  a few  of  the  basal  cells 
contract,  the  rest  of  the  tentacle  remaining  straight. 

A third  view  maintained  by  some  physiologists, 


258 


DROSERA  ROTUNDIFOLIA. 


Chap.  X 


though  rejected  by  most  others,  is  that  the  whole  cell, 
including  the  walls,  actively  contracts.  If  the  walls  are 
composed  solely  of  non-nitrogenous  cellulose,  this  view 
is  highly  improbable;  but  it  can  hardly  be  doubted 
that  they  must  be  permeated  by  proteid  matter,  at 
least  whilst  they  are  growing.  Nor  does  there  seem 
any  inherent  improbability  in  the  cell- walls  of  Drosera 
contracting,  considering  their  high  state  of  organisa- 
tion ; as  shown  in  the  case  of  the  glands  by  their  power 
of  absorption  and  secretion,  and  by  being  exquisitely 
sensitive  so  as  to  be  affected  by  the  pressure  of  the 
most  minute  particles.  The  cell-walls  of  the  pedicels 
also  allow  various  impulses  to  pass  through  them, 
inducing  movement,  increased  secretion  and  aggrega- 
tion. On  the  whole  the  belief  that  the  walls  of  certain 
cells  contract,  some  of  their  contained  fluid  being  at 
the  same  time  forced  outwards,  perhaps  accords  best 
with  the  observed  facts.  If  this  view  is  rejected,  the 
next  most  probable  one  is  that  the  fluid  contents  of 
the  cells  shrink,  owing  to  a change  in  their  molecular 
state,  with  the  consequent  closing  in  of  the  walls. 
Anyhow,  the  movement  can  hardly  be  attributed  to 
the  elasticity  of  the  walls,  together  with  a previous 
state  of  tension. 

With  respect  to  the  nature  of  the  motor  impulse 
which  is  transmitted  from  the  glands  down  the  pedi- 
cels and  across  the  disc,  it  seems  not  improbable  that 
it  is  closely  allied  to  that  influence  which  causes  the 
protoplasm  within  the  cells  of  the  glands  and  ten- 
tacles to  aggregate.  We  have  seen  that  both  forces 
originate  in  and  proceed  from  the  glands  within  a 
few  seconds  of  the  same  time,  and  are  excited  by  the 
same  causes.  The  aggregation  of  the  protoplasm  lasts 
almost  as  long  as  the  tentacles  remain  inflected, 
even  though  this  be  for  more  than  a week ; but  the 


Chap.  X. 


NATURE  OF  THE  MOTOR  IMPULSE. 


259 


protoplasm  is  redissolved  at  the  bending  place  shortly 
before  the  tentacles  re-expand,  showing  that  the  ex- 
citing cause  of  the  aggregating  process  has  then  quite 
ceased.  Exposure  to  carbonic  acid  causes  both  the 
latter  process  and  the  motor  impulse  to  travel  very 
slowly  down  the  tentacles.  We  know  that  the  aggre- 
gating process  is  delayed  in  passing  through  the  cell- 
walls,  and  we  have  good  reason  to  believe  that  this 
holds  good  with  the  motor  impulse ; for  we  can  thus 
understand  the  different  rates  of  its  transmission  in  a 
longitudinal  and  transverse  line  across  the  disc.  Under 
a high  power  the  first  sign  of  aggregation  is  the  ap- 
pearance of  a cloud,  and  soon  afterwards  of  extremely 
fine  granules,  in  the  homogeneous  purple  fluid  within 
the  cells ; and  this  apparently  is  due  to  the  union  of 
molecules  of  protoplasm.  Now  it  does  not  seem  an 
improbable  view  that  the  same  tendency — namely  for 
the  molecules  to  approach  each  other — should  be  com-, 
municated  to  the  inner  surfaces  of  the  cell-walls  which 
are  in  contact  with  the  protoplasm ; and  if  so,  their 
molecules  would  approach  each  other,  and  the  cell-wall 
would  contract. 

To  this  view  it  may  with  truth  be  objected  that 
when  leaves  are  immersed  in  various  strong  solu- 
tions, or  are  subjected  to  a heat  of  above  130° 
Fahr.  (54°*4  Cent.),  aggregation  ensues,  but  there  is 
no  movement.  Again,  various  acids  and  some  other 
fluids  cause  rapid  movement,  but  no  aggregation,  or 
only  of  an  abnormal  nature,  or  only  after  a long 
interval  of  time  ; but  as  most  of  these  fluids  are  more 
or  less  injurious,  they  may  check  or  prevent  the  aggre- 
gating process  by  injuring  or  killing  the  protoplasm. 
There  is  another  and  more  important  difference  in  the 
two  processes : when  the  glands  on  the  disc  are  ex- 
cited, they  transmit  some  influence  up  the  surrounding 


260 


DROSEEA  ROTUNDIFOLIA. 


Chap.  X. 


tentacles,  which  acts  on  the  cells  at  the  bending  place, 
but  does  not  induce  aggregation  until  it  has  reached 
the  glands ; these  then  send  back  some  other  in- 
fluence, causing  the  protoplasm  to  aggregate,  first  in 
the  upper  and  then  in  the  lower  cells. 

The  Be-expa7ision  of  the  Tentacles. — This  moyement  is 
always  slow  and  gradual.  When  the  centre  of  the 
leaf  is  excited,  or  a leaf  is  immersed  in  a proper  solu- 
tion, all  the  tentacles  bend  directly  towards  the  centre, 
and  afterwards  directly  back  from  it.  But  when  the 
point  of  excitement  is  on  one  side  of  the  disc,  the 
surrounding  tentacles  bend  towards  it,  and  therefore 
obliquely  with  respect  to  their  normal  direction ; when 
they  afterwards  re-expand,  they  bend  obliquely  back, 
so  as  to  recover  their  original  positions.  The  ten- 
tacles farthest  from  an  excited  point,  wherever  that 
may  be,  are  the  last  and  the  least  affected,  and  probably 
in  consequence  of  this  they  are  the  first  to  re-expand. 
The  bent  portion  of  a closely  inflected  tentacle  is  in  a 
state  of  active  contraction,  as  shown  by  the  following 
experiment.  Meat  was  placed  on  a leaf,  and  after  the 
tentacles  were  closely  inflected  and  had  quite  ceased  to 
move,  narrow  strips  of  the  disc,  with  a few  of  the  outer 
tentacles  attached  to  it,  were  cut  off  and  laid  on  one 
side  under  the  microscope.  After  several  failures,  I 
succeeded  in  cutting  off  the  convex  surface  of  the  bent 
portion  of  a tentacle.  Movement  immediately  recom- 
menced, and  the  already  greatly  bent  portion  went  on 
bending  until  it  formed  a perfect  circle ; the  straight 
distal  portion  of  the  tentacle  passing  on  one  side  of  the 
strip.  The  convex  surface  must  therefore  have  pre- 
viously been  in  a state  of  tension,  suflScient  to  counter- 
balance that  of  the  concave  surface,  which,  when  free, 
curled  into  a complete  ring. 

The  tentacles  of  an  expanded  and  unexcited  leaf 


Chap.  X.  EE-EXPANSION  OF  THE  TENTACLES. 


261 


are  moderately  rigid  and  elastic ; if  bent  by  a needle, 
the  upper  end  yields  more  easily  than  the  basal  and 
thicker  part,  which  alone  is  capable  of  becoming  in- 
flected. The  rigidity  of  this  basal  part  seems  due  to 
the  tension  of  the  outer  surface  balancing  a state  of 
active  and  persistent  contraction  of  the  cells  of  the 
inner  surface.  I believe  that  this  is  the  case,  because, 
when  a leaf  is  dipped  into  boiling  water,  the  tentacles 
suddenly  become  reflexed,  and  this  apparently  indi- 
cates that  the  tension  of  the  outer  surface  is  mecha- 
nical, whilst  that  of  the  inner  surface  is  vital,  and  is 
instantly  destroyed  by  the  boiling  water.  We  can 
thus  also  understand  why  the  tentacles  as  they  grow 
old  and  feeble  slowly  become  much  reflexed.  If  a 
leaf  with  its  tentacles  closely  inflected  is  dipped  into 
boiling  water,  these  rise  up  a little,  but  by  no  means 
fully  re-expand.  This  may  be  owing  to  the  heat 
quickly  destroying  the  tension  and  elasticity  of  the 
cells  of  the  convex  surface ; but  I can  hardly  believe 
that  their  tension,  at  any  one  time,  would  suffice  to 
carry  back  the  tentacles  to  their  original  position, 
often  through  an  angle  of  above  180^.  It  is  more 
probable  that  fluid,  which  we  know  travels  along  the 
tentacles  during  the  act  of  inflection,  is  slowly  re- 
attracted into  the  cells  of  the  convex  surface,  their 
tension  being  thus  gradually  and  continually  in- 
creased. 

A recapitulation  of  the  chief  facts  and  discussions 
in  this  chapter  will  be  given  at  the  close  of  the  next 
r bap  ter. 


262  DEOSERA  EOTUNDIFOLIA.  Chap,  XL 

'\ 

) ■ 

CHAPTER  XI. 

Recapitulation  of  the  Chief  Observations  on 
Drosera  rotundifolia. 

As  summaries  have  been  given  to  most  of  the 
chapters,  it  will  be  sufficient  here  to  recapitulate,  as 
briefly  as  I can,  the  chief  points.  In  the  first  chapter 
a preliminary  sketch  was  given  of  the  structure  of  the 
leaves,  and  of  the  manner  in  which  they  capture 
insects.  This  is  effected  by  drops  of  extremely  viscid 
fluid  surrounding  the  glands  and  by  the  inward 
movement  of  the  tentacles.  As  the  plants  gain  most 
of  their  nutriment  by  this  means,  their  roots  are  very 
poorly  developed;  and  they  often  grow  in  places 
where  hardly  any  other  plant  except  mosses  can 
exist.  The  glands  have  the  power  of  absorption, 
besides  that  of  secretion.  They  are  extremely  sen- 
sitive to  various  stimulants,  namely  repeated  touches, 
the  pressure  of  minute  particles,  the  absorption  of 
animal  matter  and  of  various  fluids,  heat,  and  gal- 
vanic action.  A tentacle  with  a bit  of  raw  meat  on 
the  gland  has  been  seen  to  begin  bending  in  10  s., 
to  be  strongly  incurved  in  5 m.,  and  to  reach  the 
centre  of  the  leaf  in  half  an  hour.  The  blade  of  the 
leaf  often  becomes  so  much  inflected  that  it  forms  a 
cup,  enclosing  any  object  placed  on  it. 

A gland,  when  excited,  not  only  sends  some  in- 
fluence down  its  own  tentacle,  causing  it  to  bend,  but 
likewise  to  the  surrounding  tentacles,  which  become 
incurved ; so  that  the  bending  place  can  be  acted  on 
by  an  impulse  received  from  opposite  directions, 


Chap.  XI 


GENERAL  SUMMARY. 


263 


namely  from  the  gland  on  the  summit  of  the  same 
tentacle,  and  from  one  or  more  glands  of  the  neigh- 
bouring tentacles.  Tentacles,  when  inflected,  re-ex- 
pand  after  a time,  and  during  this  process  the  glands 
secrete  less  copiously,  or  become  dry.  As  soon  as 
they  begin  to  secrete  again,  the  tentacles  are  ready 
to  re-act ; and  this  may  be  repeated  at  least  three, 
probably  many  more  times. 

It  was  shown  in  the  second  chapter  that  animal  sub- 
stances placed  on  the  discs  cause  much  more  prompt 
and  energetic  inflection  than  do  inorganic  bodies  of 
the  same  size,  or  mere  mechanical  irritation;  but 
there  is  a still  more  marked  difference  in  the  greater 
length  of  time  during  which  the  tentacles  remain  in- 
flected over  bodies  yielding  soluble  and  nutritious 
matter,  than  over  those  which  do  not  yield  such 
matter.  Extremely  minute  particles  of  glass,  cinders, 
hair,  thread,  precipitated  chalk,  &c.,  when  placed  on 
the  glands  of  the  outer  tentacles,  cause  them  to  bend. 
A particle,  unless  it  sinks  through  the  secretion  and 
actually  touches  the  surface  of  the  gland  with  some 
one  point,  does  not  produce  any  effect.  A little  bit 
of  thin  human  hair  tAt  ii^ch  (*203  mm.)  in 

length,  and  weighing  only  y-g  o*  of  a grain  (*000822 
mg.),  though  largely  supported  by  the  dense  secre- 
tion, suffices  to  induce  movement.  It  is  not  probable 
that  the  pressure  in  this  case  could  have  amounted 
to  that  from  the  millionth  of  a grain.  Even  smaller 
particles  cause  a slight  movement,  as  could  be  seen 
through  a lens.  Larger  particles  than  those  of  which 
the  measurements  have  been  given  cause  no  sensation 
when  placed  on  the  tongue,  one  of  the  most  sensitive 
parts  of  the  human  body. 

Movement  ensues  if  a gland  is  momentarily  touched 
three  or  four  times ; but  if  touched  only  once  or  twice. 


264 


DKOSERA  ROTUNDIJFOLIA. 


Chap.  XI. 


though  with  considerable  force  and  with  a hard  object, 
the  tentacle  does  not  bend.  The  plant  is  thus  saved 
from  much  useless  movement,  as  during  a high  wind 
the  glands  can  hardly  escape  being  occasionally 
brushed  by  the  leaves  of  surrounding  plants.  Though 
insensible  to  a single  touch,  they  are  exquisitely  sensi- 
tive, as  just  stated,  to  the  slightest  pressure  if  pro- 
longed for  a few  seconds ; and  this  capacity  is  mani- 
festly of  service  to  the  plant  in  capturing  small 
insects.  Even  gnats,  if  they  rest  on  the  glands  with 
their  delicate  feet,  are  quickly  and  securely  embraced. 
The  glands  are  insensible  to  the  weight  and  repeated 
blows  of  drops  of  heavy  rain,  and  the  plants  are  thus 
likewise  saved  from  much  useless  movement. 

The  description  of  the  movements  of  the  tentacles 
was  interrupted  in  the  third  chapter  for  the  sake  of 
describing  the  process  of  aggregation.  This  process 
always  commences  in  the  cells  of  the  glands,  the  con- 
tents of  which  first  become  cloudy ; and  this  has 
been  observed  within  10  s.  after  a gland  has  been 
excited.  Granules  just  resolvable  under  a very  high 
power  soon  appear,  sometimes  within  a minute,  in  the 
cells  beneath  the  glands ; and  these  then  aggregate 
into  minute  spheres.  The  process  afterwards  travels 
down  the  tentacles,  being  arrested  for  a short  time  at 
each  transverse  partition.  The  small  spheres  coalesce 
into  larger  spheres,  or  into  oval,  club-headed,  thread- 
er necklace-like,  or  otherwise  shaped  masses  of  proto- 
plasm, which,  suspended  in  almost  colourless  fluid, 
exhibit  incessant  spontaneous  changes  of  form.  These 
frequently  coalesce  and  again  separate.  If  a gland 
has  been  powerfully  excited,  all  the  cells  down  to  the 
base  of  the  tentacle  are  affected.  In  cells,  especially 
if  filled  with  dark  red  fluid,  the  first  step  in  the 


Chap.  XI. 


GENERAL  SUMMARY. 


265 


process  often  is  the  formation  of  a dark  red,  bag- 
like mass  of  protoplasm,  which  afterwards  divides 
and  undergoes  the  usual  repeated  changes  of  form. 
Before  any  aggregation  has  been  excited,  a sheet  of 
colourless  protoplasm,  including  granules  (the  prim- 
ordial utricle  of  Mohl),  flows  round  the  walls  of  the 
cells;  and  this  becomes  more  distinct  after  the  con- 
tents have  been  partially  aggregated  into  spheres 
or  bag-like  masses.  But  after  a time  the  granules 
are  drawn  towards  the  central  masses  and  unite  with 
them;  and  then  the  circulating  sheet  can  no  longer 
be  distinguished,  but  there  is  still  a current  of  trans- 
parent fluid  within  the  cells. 

Aggregation  is  excited  by  almost  all  the  stimulants 
which  induce  movement;  such  as  the  glands  being 
touched  two  or  three  times,  the  pressure  of  minute 
inorganic  particles,  the  absorption  of  various  fluids, 
even  long  immersion  in  distilled  water,  exosmose,  and 
heat.  Of  the  many  stimulants  tried,  carbonate  of 
ammonia  is  the  most  energetic  and  acts  the  quickest : 
a dose  of  ^ grain  (*00048  mg.)  given  to 

a single  gland  suffices  to  cause  in  one  hour  well- 
marked  aggregation  in  the  upper  cells  of  the  tentacle. 
The  process  goes  on  only  as  long  as  the  protoplasm 
is  in  a living,  vigorous,  and  oxygenated  condition. 

The  result  is  in  all  respects  exactly  the  same, 
whether  a gland  has  been  excited  directly,  or  has 
received  an  influence  from  other  and  distant  glands. 
But  there  is  one  important  dijfference : when  the 
central  glands  are  irritated,  they  transmit  centri- 
fugally  an  influence  up  the  pedicels  of  the  exterior 
tentacles  to  their  glands;  but  the  actual  process  of 
aggregation  travels  centripetally,  from  the  glands  of 
the  exterior  tentacles  down  their  pedicels.  The  ex- 
citing influence,  therefore,  which  is  transmitted  from 


266 


DROSERA  ROTUNDIFOLIA. 


Chap.  XL 


one  part  of  the  leaf  to  another  must  be  different 
from  that  which  actually  induces  aggregation.  The 
process  does  not  depend  on  the  glands  secreting 
more  copiously  than  they  did  before  ; and  is  inde- 
pendent of  the  inflection  of  the  tentacles.  It  con- 
tinues as  long  as  the  tentacles  remain  inflected,  and  as 
soon  as  these  are  fully  re-expanded,  the  little  masses 
of  protoplasm  are  all  redissolved ; the  cells  becoming 
filled  with  homogeneous  purple  fluid,  as  they  were 
before  the  leaf  was  excited. 

As  the  process  of  aggregation  can  be  excited  by  a 
few  touches,  or  by  the  pressure  of  insoluble  particles, 
it  is  evidently  independent  of  the  absorption  of  any 
matter,  and  must  be  of  a molecular  nature.  Even  when 
caused  by  the  absorption  of  the  carbonate  or  other 
salt  of  ammonia,  or  an  infusion  of  meat,  the  process 
seems  to  be  of  exactly  the  same  nature.  The  proto- 
plasmic fluid  must,  therefore,  be  in  a singularly  un- 
stable condition,  to  be  acted  on  by  such  slight  and 
varied  causes.  Physiologists  believe  that  when  a 
nerve  is  touched,  and  it  transmits  an  influence  to  other 
parts  of  the  nervous  system,  a molecular  change  is 
induced  in  it,  though  not  visible  to  us.  Therefore  it 
is  a very  interesting  spectacle  to  watch  the  effects  on 
the  cells  of  a gland,  of  the  pressure  of  a bit  of  hair, 
weighing  only  y-^  o-o  of  a grain  and  largely  supported 
by  the  dense  secretion,  for  this  excessively  slight 
pressure  soon  causes  a visible  change  in  the  proto- 
plasm, which  change  is  transmitted  down  the  whole 
length  of  the  tentacle,  giving  it  at  last  a mottled 
appearance,  distinguishable  even  by  the  naked  eye. 

In  the  fourth  chapter  it  was  shown  that  leaves 
placed  for  a short  time  in  water  at  a temperature  of 
110"^  Eahr.  (43°*3  Cent.)  become  somewhat  inflected ; 
they  are  thus  also  rendered  more  sensitive  to  the  action 


Chap.  XL 


GENERAL  SUMMARY. 


267 


of  meat  than  they  were  before.  If  exposed  to  a tem- 
perature of  between  115°  and  125°  (46°*1 — 51°*6  Cent.), 
they  are  quickly  inflected,  and  their  protoplasm  under- 
goes aggregation ; when  afterwards  placed  in  cold  water, 
they  re-expand.  Exposed  to  130°  (54°*4  Cent.),  no  in- 
flection immediately  occurs,  but  the  leaves  are  only 
temporarily  paralysed,  for  on  being  left  in  cold  water, 
they  often  become  inflected  and  afterwards  re-expand. 
In  one  leaf  thus  treated,  I distinctly  saw  the  protoplasm 
in  movement.  In  other  leaves,  treated  in  the  same 
manner,  and  then  immersed  in  a solution  of  carbonate 
of  ammonia,  strong  aggregation  ensued.  Leaves  placed 
in  cold  water,  after  an  exposure  to  so  high  a tem- 
perature as  145°  (62°*7  Cent.),  sometimes  become 
slightly,  though  slowly,  inflected ; and  afterwards  have 
the  contents  of  their  cells  strongly  aggregated  by  car- 
bonate of  ammonia.  But  the  duration  of  the  immer- 
sion is  an  important  element,  for  if  left  in  water  at 
145°  (62°*7  Cent.),  or  only  at  140°  (60°  Cent.),  until  it 
becomes  cool,  they  are  killed,  and  the  contents  of  the 
glands  are  rendered  white  and  opaque.  This  latter 
result  seems  to  be  due  to  the  coagulation  of  the  albu- 
men, and  was  almost  always  caused  by  even  a short 
exposure  to  150°  (65°*5  Cent.) ; but  different  leaves,  and 
even  the  separate  cells  in  the  same  tentacle,  differ  con- 
siderably in  their  power  of  resisting  heat.  Unless  the 
heat  has  been  sufficient  to  coagulate  the  albumen,  car- 
bonate of  ammonia  subsequently  induces  aggregation. 

In  the  fifth  chapter,  the  results  of  placing  drops  of 
various  nitrogenous  and  non-nitrogenous  organic  fluids 
on  the  discs  of  leaves  were  given,  and  it  was  shown 
that  they  detect  with  almost  unerring  certainty  the 
presence  of  nitrogen.  A decoction  of  green  peas  or 
of  fresh  cabbage-leaves  acts  almost  as  powerfully  as  an 
infusion  of  raw  meat ; whereas  an  infusion  of  cabbage- 


268 


DKOSERA  ROTUNDIFOLIA. 


Chap.  XI. 


leaves  made  by  keeping  them  for  a long  time  in 
merely  warm  water  is  far  less  efficient.  A decoction 
of  grass-leaves  is  less  powerful  than  one  of  green  peas 
or  cabbage-leaves. 

These  results  led  me  to  inquire  whether  Drosera 
possessed  the  power  of  dissolving  solid  animal  matter. 
The  experiments  proving  that  the  leaves  are  capable 
of  true  digestion,  and  that  the  glands  absorb  the  di- 
gested matter,  are  given  in  detail  in  the  sixth  chapter. 
These  are,  perhaps,  the  most  interesting  of  all  my 
observations  on  Drosera,  as  no  such  power  was  before 
distinctly  known  to  exist  in  the  vegetable  kingdom. 
It  is  likewise  an  interesting  fact  that  the  glands  of  the 
disc,  when  irritated,  should  transmit  some  influence 
to  the  glands  of  the  exterior  tentacles,  causing  them 
to  secrete  more  copiously  and  the  secretion  to  be- 
come acid,  as  if  they  had  been  directly  excited  by 
an  object  placed  on  them.  The  gastric  juice  pf  ani^ 
mals  contains,  as  is  well  known,  an  acid  and  a fer- 
ment, both  of  which  are  indispensable  for  digestion, 
and  so  it  is  with  the  secretion  of  Drosera.  When  the 
stomach  of  an  animal  is  mechanically  irritated,  it 
secretes  an  acid,  and  when  particles  of  glass  or  other 
such  objects  were  placed  on  the  glands  of  Drosera, 
the  secretion,  and  that  of  the  surrounding  and  un- 
touched glands,  was  increased  in  quantity  and  became 
acid.  But,  according  to  Schifif,  the  stomach  of  an 
animal  does  not  secrete  its  proper  ferment,  pepsin, 
until  certain  substances,  which  he  calls  peptogenes, 
are  absorbed;  and  it  appears  from  my  experiments 
that  some  matter  must  be  absorbed  by  the  glands 
of  Drosera  before  they  secrete  their  proper  ferment. 
That  the  secretion  does  contain  a ferment  which  acts 
only  in  the  presence  of  an  acid  on  solid  animal 
matter,  was  clearly  proved  by  adding  minute  doses  of 


Chap.  XI. 


GENERAL  SUMMARY. 


269 


an  alkali,  which  entirely  arrested  the  process  of  diges- 
tion, this  immediately  recommencing  as  soon  as  the 
alkali  was  neutralised  by  a little  weak  hydrochloric 
acid.  From  trials  made  with  a large  number  of 
substances,  it  was  found  that  those  which  the  secretion 
of  Drosera  dissolves  completely,  or  partially,  or  not 
at  all,  are  acted  on  in  exactly  the  same  manner  by 
gastric  juice.  We  may,  therefore,  conclude  that  the 
ferment  of  Drosera  is  closely  analogous  to,  or  identical 
with,  the  pepsin  of  animals. 

The  substances  which  are  digested  by  Drosera  act 
on  the  leaves  very  differently.  Some  cause  much 
more  energetic  and  rapid  inflection  of  the  tentacles, 
and  keep  them  inflected  for  a much  longer  time,  than 
do  others.  We  are  thus  led  to  believe  that  the 
former  are  more  nutritious  than  the  latter,  as  is 
known  to  be  the  case  with  some  of  these  same  sub- 
stances when  given  to  animals ; for  instance,  meat  in 
comparison  with  gelatine.  As  cartilage  is  so  tough  a 
substance  and  is  so  little  acted  on  by  water,  its 
prompt  dissolution  by  the  secretion  of  Drosera,  and 
subsequent  absorption,  is,  perhaps,  one  of  the  most 
striking  cases.  But  it  is  not  really  more  remarkable 
than  the  digestion  of  meat,  which  is  dissolved  by  this 
secretion  in  the  same  manner  and  by  the  same  stages 
as  by  gastric  juice.  The  secretion  dissolves  bone,  and 
even  the  enamel  of  teeth,  but  this  is  simply  due  to 
the  large  quantity  of  acid  secreted,  owing,  apparently, 
to  the  desire  of  the  plant  for  phosphorus.  In  the 
case  of  bone,  the  ferment  does  not  come  into  play 
until  all  the  phosphate  of  lime  has  been  decomposed 
and  free  acid  is  present,  and  then  the  fibrous  basis  is 
quickly  dissolved.  Lastly,  the  secretion  attacks  and 
dissolves  matter  out  of  living  seeds,  which  it  some- 
times kills,  or  injures,  as  shown  by  the  diseased  state 


270 


DROSERA  ROTUNDIFOLIA. 


Chap.  XI 


of  the  seedlings.  It  also  absorbs  matter  from  pollen, 
and  from  fragments  of  leaves. 

The  seventh  chapter  was  devoted  to  the  action  of 
the  salts  of  ammonia.  These  all  cause  the  tentacles, 
and  often  the  blade  of  the  leaf,  to  be  inflected,  and 
the  protoplasm  to  be  aggregated.  They  act  with  very 
different  power ; the  citrate  being  the  least  powerful, 
and  the  phosphate,  owing,  no  doubt,  to  the  presence 
of  phosphorus  and  nitrogen,  by  far  the  most  powerful. 
But  the  relative  efliciency  of  only  three  salts  of 
ammonia  was  carefully  determined,  namely  the  car- 
bonate, nitrate,  and  phosphate.  The  experiments  were 
made  by  placing  half-minims  (-0296  ml.)  of  solutions 
of  different  strengths  on  the  discs  of  the  leaves, — by 
applying  a minute  drop  (about  the  of  a minim,  or 
•00296  ml.)  for  a few  seconds  to  three  or  four  glands,— r 
and  by  the  immersion  of  whole  leaves  in  a measured 
quantity.  In  relation  to  these  experiments  it  was 
necessary  first  to  ascertain  the  effects  of  distilled  water, 
and  it  was  found,  as  described  in  detail,  that  the  more 
sensitive  leaves  are  affected  by  it,  but  only  in  a slight 
degree. 

A solution  of  the  carbonate  is  absorbed  by  the  roots 
and  induces  aggregation  in  their  cells,  but  does  not 
affect  the  leaves.  The  vapour  is  absorbed  by  the 
glands,  and  causes  inflection  as  well  as  aggregation. 
A drop  of  a solution  containing  of  a grain 
(*0675  mg.)  is  the  least  quantity  which,  when  placed 
on  the  glands  of  the  disc,  excites  the  exterior  ten- 
tacles to  bend  inwards.  But  a minute  drop,  contain- 
iiig  T4T-00-  of  ^ grain  (*00445  mg.),  if  applied  for  a few 
seconds  to  the  secretion  surrounding  a gland,  causes 
the  inflection  of  the  same  tentacle.  When  a highly 
sensitive  leaf  is  immersed  in  a solution,  and  there  is 
ample  time  for  absorption,  the  irg-8*8-o  o of  a grain 


Chap.  XI. 


GENEKAL  SUMMARY. 


271 


(*00024  mg.)  is  sufficient  to  excite  a single  tentacle 
into  movement. 

The  nitrate  of  ammonia  induces  aggregation  of  the 
protoplasm  much  less  quickly  than  the  carbonate,  but 
is  more  potent  in  causing  inflection.  A drop  contain- 
ing -^Vo-  of  a grain  (*027  mg.)  placed  on  the  disc  acts 
powerfully  on  all  the  exterior  tentacles,  which  have 
not  themselves  received  any  of  the  solution  ; whereas  a 
drop  with  -^Vo  of  a grain  caused  only  a few  of  these 
tentacles  to  bend,  but  affected  rather  more  plainly  the 
blade.  A minute  drop  applied  as  before,  and  contain- 
vTWo  of  a grain  (*0025  mg.),  caused  the  tentacle 
bearing  this  gland  to  bend.  By  the  immersion  of 
whole  leaves,  it  was  proved  that  the  absorption  by  a 
single  gland  of  of  a grain  (*0000937  mg.)  was 

sufficient  to  set  the  same  tentacle  into  movement. 

The  phosphate  of  ammonia  is  much  more  powerful 
than  the  nitrate.  A drop  containing  3VT-0  of  a grain 
(*0169  mg.)  placed  on  the  disc  of  a sensitive  leaf 
causes  most  of  the  exterior  tentacles  to  be  inflected, 
as  well  as  the  blade  of  the  leaf.  A minute  drop  con- 
taining ttsV-to  of  a grain  (*000423  mg.),  applied  for  a 
few  seconds  to  a gland,  acts,  as  shown  by  the  move- 
ment of  the  tentacle.  When  a leaf  is  immersed  in 
thirty  minims  (1*7748  ml.)  of  a solution  of  one  part  by 
weight  of  the  salt  to  21,875,000  of  water,  the  absorp- 
tion by  a gland  of  only  the  tq  t-b-q-o-q-o  of  a grain 
(*00000328  mg.),  that  is,  about  the  one-twenty-mil- 
lionth of  a grain,  is  sufficient  to  cause  the  tentacle 
bearing  this  gland  to  bend  to  the  centre  of  the 
leaf.  In  this  experiment,  owing  to  the  presence  of 
the  water  of  crystallisation,  less  than  the  one-thirty- 
millionth  of  a grain  of  the  efficient  elements  could 
have  been  absorbed.  There  is  nothing  remarkable  in 
such  minute  quantities  being  absorbed  by  the  glands, 


272 


DROSERA  ROTUN  DIFOLIA. 


Chap.  XI. 


for  all  physiologists  admit  that  the  salts  of  ammonia, 
which  must  be  brought  in  still  smaller  quantity  by  a 
single  shower  of  rain  to  the  roots,  are  absorbed  by 
them.  Nor  is  it  surprising  that  Drosera  should  be 
enabled  to  profit  by  the  absorption  of  these  salts,  for 
yeast  and  other  low  fungoid  forms  flourish  in  solutions 
of  ammonia,  if  the  other  necessary  elements  are  pre- 
sent. But  it  is  an  astonishing  fact,  on  which  I will 
not  here  again  enlarge,  that  so  inconceivably  minute  a 
quantity  as  the  one-twenty-millionth  of  a grain  of 
phosphate  of  ammonia  should  induce  some  change  in 
a gland  of  Drosera,  sufficient  to  cause  a motor  impulse 
to  be  sent  down  the  whole  length  of  the  tentacle ; this 
impulse  exciting  movement  often  through  an  angle  of 
above  180"^.  I know  not  whether  to  be  most  astonished 
at  this  fact,  or  that  the  pressure  of  a minute  bit  of 
hair,  supported  by  the  dense  secretion,  should  quickly 
cause  conspicuous  movement.  Moreover,  this  extreme 
sensitiveness,  exceeding  that  of  the  most  delicate  part 
of  the  human  body,  as  well  as  the  power  of  transmit- 
ting various  impulses  from  one  part  of  the  leaf  to 
another,  have  been  acquired  without  the  intervention 
of  any  nervous  system. 

As  few  plants  are  at  present  known  to  possess  glands 
specially  adapted  for  absorption,  it  seemed  worth  while 
to  try  the  effects  on  Drosera  of  various  other  salts, 
besides  those  of  ammonia,  and  of  various  acids.  Their 
action,  as  described  in  the  eighth  chapter,  does  not 
correspond  at  all  strictly  with  their  chemical  affinities, 
as  inferred  from  the  classification  commonly  followed. 
The  nature  of  the  base  is  far  more  influential  than 
that  of  the  acid  ; and  this  is  known  to  hold  good  with 
animals.  For  instance,  nine  salts  of  sodium  all  caused 
well-marked  inflection,  and  none  of  them  were  poison- 
ous in  small  doses ; whereas  seven  of  the  nine  corre» 


Chap.  XI. 


GENERAL  SUMMARY. 


273 


spending  salts  of  potassium  produced  no  effect,  two 
causing  slight  inflection.  Small  doses,  moreover,  of 
some  of  the  latter  salts  were  poisonous.  The  salts 
of  sodium  and  potassium,  when  injected  into  the  veins 
of  animals,  likewise  differ  widely  in  their  action.  The 
so-called  earthy  salts  produce  hardly  any  effect  on 
Drosera.  On  the  other  hand,  most  of  the  metallic 
salts  cause  rapid  and  strong  inflection,  and  are  highly 
poisonous ; but  there  are  some  odd  exceptions  to  this 
rule;  thus  chloride  of  lead  and  zinc,  as  well  as  two 
salts  of  barium,  did  not  cause  inflection,  and  were  not 
poisonous. 

Most  of  the  acids  which  were  tried,  though  much 
diluted  (one  part  to  437  of  water),  and  given  in  small 
doses,  acted  powerfully  on  Drosera ; nineteen,  out  of  the 
twenty-four,  causing  the  tentacles  to  be  more  or  less 
inflected.  Most  of  them,  even  the  organic  acids,  are 
poisonous,  often  highly  so  ; and  this  is  remarkable,  as 
the  juices  of  so  many  plants  contain  acids.  Benzoic 
acid,  which  is  innocuous  to  animals,  seems  to  be  as 
poisonous  to  Drosera  as  hydrocyanic.  On  the  other 
hand,  hydrochloric  acid  is  not  poisonous  either  to 
animals  or  to  Drosera,  and  induces  only  a moderate 
amount  of  inflection.  Many  acids  excite  the  glands  to 
secrete  an  extraordinary  quantity  of  mucus ; and  the 
protoplasm  within  their  cells  seems  to  be  often  killed, 
as  may  be  inferred  from  the  surrounding  fluid  soon 
becoming  pink.  It  is  strange  that  allied  acids  act 
very  differently : formic  acid  induces  very  slight  in- 
flection, and  is  not  poisonous ; whereas  acetic  acid  of 
the  same  strength  acts  most  powerfully  and  is  poi- 
sonous. Lactic  acid  is  also  poisonous,  but  causes 
inflection  only  after  a considerable  lapse  of  time. 
Malic  acid  acts  slightly,  whereas  citric  and  tartaric 
acids  produce  no  effect. 


274 


DROSERA  ROTUNDIFOLIA. 


Chap.  XL 


In  the  ninth  chapter  the  effects  of  the  absorption  of 
various  alkaloids  and  certain  other  substances  were 
described.  Although  some  of  these  are  poisonous,  yet 
as  several,  which  act  powerfully  on  the  nervous  system 
of  animals,  produce  no  effect  on  Drosera,  we  may  infer 
that  the  extreme  sensibility  of  the  glands,  and  their 
power  of  transmitting  an  influence  to  other  parts  of 
the  leaf,  causing  movement,  or  modified  secretion,  or 
aggregation,  does  not  depend  on  the  presence  of  a 
diffused  element,  allied  to  nerve-tissue.  One  of  the 
most  remarkable  facts  is  that  long  immersion  in  the 
poison  of  the  cobra-snake  does  not  in  the  least 
check,  but  rather  stimulates,  the  spontaneous  move- 
ments of  the  protoplasm  in  the  cells  of  the  tentacles. 
Solutions  of  various  salts  and  acids  behave  very  dif- 
ferently in  delaying  or  in  quite  arresting  the  sub- 
sequent action  of  a solution  of  phosphate  of  ammonia. 
Camphor  dissolved  in  water  acts  as  a stimulant,  as 
do  small  doses  of  certain  essential  oils,  for  they  cause 
rapid  and  strong  inflection.  Alcohol  is  not  a stimu- 
lant. The  vapours  of  camphor,  alcohol,  chloroform, 
sulphuric  and  nitric  ether,  are  poisonous  in  moderately 
large  doses,  but  in  small  doses  serve  as  narcotics  or 
ana0sthetics,  greatly  delaying  the  subsequent  action 
of  meat.  But  some  of  these  vapours  also  act  as  stimu- 
lants, exciting  rapid,  almost  spasmodic  movements  in 
the  tentacles.  Carbonic  acid  is  likewise  a narcotic, 
and  retards  the  aggregation  of  the  protoplasm  when 
carbonate  of  ammonia  is  subsequently  given.  The  first 
access  of  air  to  plants  which  have  been  immersed  in 
this  gas  sometimes  acts  as  a stimulant  and  induces 
movement.  But,  as  before  remarked,  a special  pharma- 
copoeia would  be  necessary  to  describe  the  diversified 
effects  of  various  substances  on  the  leaves  of  Drosera. 

In  the  tenth  chapter  it  was  shown  that  the  sensitive* 


Chap.  XI. 


GENERAL  SUMMARY. 


275 


ness  of  the  leaves  appears  to  be  wholly  confined  to 
the  glands  and  to  the  immediately  underlying  cells. 
It  was  further  shown  that  the  motor  impulse  and  other 
forces  or  influences,  proceeding  from  the  glands  when 
excited,  pass  through  the  cellular  tissue,  and  not  along 
the  fibro-vascular  bundles.  A gland  sends  its  motor 
impulse  with  great  rapidity  down  the  pedicel  of  the 
same  tentacle  to  the  basal  part  which  alone  bends.  The 
impulse,  then  passing  onwards,  spreads  on  all  sides  to 
the  surrounding  tentacles,  first  affecting  those  which 
stand  nearest  and  then  those  farther  off.  But  by  being 
thus  spread  out,  and  from  the  cells  of  the  disc  not 
being  so  much  elongated  as  those  of  the  tentacles,  it 
loses  force,  and  here  travels  much  more  slowly  than 
down  the  pedicels.  Owing  also  to  the  direction  and 
form  of  the  cells,  it  passes  with  greater  ease  and  cele- 
rity in  a longitudinal  than  in  a transverse  line  across 
the  disc.  The  impulse  proceeding  from  the  glands  of 
the  extreme  marginal  tentacles  does  not  seem  to  have 
force  enough  to  affect  the  adjoining  tentacles ; and 
this  may  be  in  part  due  to  their  length.  The  impulse 
from  the  glands  of  the  next  few  inner  rows  spreads 
chiefly  to  the  tentacles  on  each  side  and  towards  the 
centre  of  the  leaf ; but  that  proceeding  from  the  glands 
of  the  shorter  tentacles  on  the  disc  radiates  almost 
equally  on  all  sides. 

When  a gland  is  strongly  excited  by  the  quantity 
or  quality  of  the  substance  placed  on  it,  the  motor 
impulse  travels  farther  than  from  one  slightly  excited ; 
and  if  several  glands  are  simultaneously  excited,  the 
impulses  from  all  unite  and  spread  still  farther.  As 
soon  as  a gland  is  excited,  it  discharges  an  impulse 
which  extends  to  a considerable  distance ; but  after- 
wards, whilst  the  gland  is  secreting  and  absorbing, 
the  impulse  suffices  only  to  keep  the  same  tentacle 


276 


DROSERA  ROTUNDIFOLIA. 


Chap.  XL 


inflected ; though  the  inflection  may  last  for  many 
days. 

If  the  bending  place  of  a tentacle  receives  an  impulse 
from  its  own  gland,  the  movement  is  always  towards 
the  centre  of  the  leaf;  and  so  it  is  with  all  the 
tentacles,  when  their  glands  are  excited  by  immer- 
sion in  a proper  fluid.  The  short  ones  in  the  middle 
part  of  the  disc  must  be  excepted,  as  these  do  not 
bend  at  all  when  thus  excited.  On  the  other  hand, 
when  the  motor  impulse  comes  from  one  side  of  the 
disc,  the  surrounding  tentacles,  including  the  short 
ones  in  the  middle  of  the  disc,  all  bend  with  pre- 
cision towards  the  point  of  excitement,  wherever  this 
may  be  seated.  This  is  in  every  way  a remarkable 
phenomenon ; for  the  leaf  falsely  appears  as  if  en- 
dowed with  the  senses  of  an  animal.  It  is  all  the 
more  remarkable,  as  when  the  motor  impulse  strikes 
the  base  of  a tentacle  obliquely  with  respect  to  its 
flattened  surface,  the  contraction  of  the  cells  must  be 
confined  to  one,  two,  or  a very  few  rows  at  one  end. 
And  different  sides  of  the  surrounding  tentacles  must 
be  acted  on,  in  order  that  all  should  bend  with  pre- 
cision to  the  point  of  excitement. 

The  motor  impulse,  as  it  spreads  from  one  or  more 
glands  across  the  disc,  enters  the  bases  of  the  sur- 
rounding tentacles,  and  immediately  acts  on  the  bend- 
ing place.  It  does  not  in  the  first  place  proceed  up 
the  tentacles  to  the  glands,  exciting  them  to  reflect 
back  an  impulse  to  their  bases.  Nevertheless,  some 
influence  is  sent  up  to  the  glands,  as  their  secre- 
tion is  soon  increased  and  rendered  acid;  and  then 
the  glands,  being  thus  excited,  send  back  some  other 
influence  (not  dependent  on  increased  secretion,  nor 
on  the  inflection  of  the  tentacles),  causing  the  proto- 
plasm to  aggregate  in  cell  beneath  cell.  This  may 


Chap.  XL 


GENERAL  SUMMARY. 


277 


be  called  a reflex  action,  though  probably  very  dif- 
ferent from  that  proceeding  from  the  nerve-ganglion 
of  an  animal ; and  it  is  the  only  known  case  of  reflex 
action  in  the  vegetable  kingdom. 

About  the  mechanism  of  the  movements  and  the 
nature  of  the  motor  impulse  we  know  very  little. 
During  the  act  of  inflection  fluid  certainly  travels  from 
one  part  to  another  of  the  tentacles.  But  the  hypo- 
thesis which  agrees  best  with  the  observed  facts  is 
that  the  motor  impulse  is  allied  in  nature  to  the 
aggregating  process ; and  that  this  causes  the  mole- 
cules of  the  cell-walls  to  approach  each  other,  in  the 
same  manner  as  do  the  molecules  of  the  protoplasm 
within  the  cells  ; so  that  the  cell-walls  contract.  But 
some  strong  objections  may  be  urged  against  this  view. 
The  re-expansion  of  the  tentacles  is  largely  due  to 
the  elasticity  of  their  outer  cells,  which  comes  into 
play  as  soon  as  those  on  the  inner  side  cease  con- 
tracting with  prepotent  force ; but  we  have  reason  to 
suspect  that  fluid  is  continually  and  slowly  attracted 
into  the  outer  cells  during  the  act  of  re-expansion, 
thus  increasing  their  tension. 

I have  now  given  a brief  recapitulation  of  the  chief 
points  observed  by  me,  with  respect  to  the  struc- 
ture, movements,  constitution,  and  habits  of  Drosera 
rotundifolia  ; and  we  see  how  little  has  been  made  out 
in  comparison  with  what  remains  unexplained  and 
unknown. 


278 


DROSEEA  ANGLIOA. 


ChJlP.XIL 


CHAPTEE  XII. 

On  the  Structuke  and  Movements  op  some  other  Species  op 
Drosera. 

Drosera  anglica  — Drosera  intermedia  — Drosera  eapensis — Drosera 
spathulata  — Drosera  filiformis  — Drosera  hinata  — Concluding 
remarks. 

I EXAMINED  six  other  species  of  Drosera,  some  of 
them  inhabitants  of  distant  countries,  chiefly  for  the 
sake  of  ascertaining  whether  they  caught  insects.  This 
seemed  the  more  necessary  as  the  leaves  of  some  of 
the  species  differ  to  an  extraordinary  degree  in  shape 
from  the  rounded  ones  of  Drosera  rotundifolia.  In 
functional  powers,  however,  they  differ  very  little. 

Drosera  anglica  (Hudson).* — The  leaves  of  this  species,  which 
was  sent  to  me  from  Ireland,  are  much  elongated,  and  gradually 
widen  from  the  footstalk  to  the  bluntly  pointed  apex.  They 
stand  almost  erect,  and  their  blades  sometimes  exceed  1 inch 
in  length,  whilst  their  breadth  is  only  the  ^ of  an  inch.  The 
glands  of  all  the  tentacles  have  the  same  structure,  so  that  the 
extreme  marginal  ones  do  not  differ  from  the  others,  as  in  the 
case  of  Drosera  rotundifolia.  When  they  are  irritated  by  being 
roughly  touched,  or  by  the  pressure  of  minute  inorganic  par- 
ticles, or  by  contact  with  animal  matter,  or  by  the  absorption  of 
carbonate  of  ammonia,  the  tentacles  become  inflected ; the  basal 
portion  being  the  chief  seat  of  movement.  Cutting  or  pricking 
the  blade  of  the  leaf  did  not  excite  any  movement.  They  fre- 
quently capture  insects,  and  the  glands  of  the  inflected  tentacles 
pour  forth  much  acid  secretion.  Bits  of  roast  meat  were  placed 
on  some  glands,  and  the  tentacles  began  to  move  in  1 m.  or 


* Mrs.  Treat  has  given  an  ex-  synonym  in  part  of  Drosera  an- 
cellent  account  in  ‘ The  American  glica),  of  Drosera  rotundifolia  and 
Naturalist/  December'lSTSjp.TOS,  filiformis, 
of  Drosera  longifolia  (which  is  a 


Ohap.  Xll. 


DROSERA  CAPENSIS. 


279 


1 m.  30  s. ; and  in  1 hr.  10  m.  reached  the  centre.  Two  bits  of 
boiled  cork,  one  of  boiled  thread,  and  two  of  coal-cinders  taken 
from  the  fire,  were  placed,  by  the  aid  of  an  instrument  which 
had  been  immersed  in  boiling  water,  on  five  glands ; these  super- 
fluous precautions  having  been  taken  on  account  of  M.  Ziegler's 
statements.  One  of  the  particles  of  cinder  caused  some  inflection 
in  8 hrs.  45  m.,  as  did  after  23  hrs.  the  other  particle  of  cinder, 
the  bit  of  thread,  and  both  bits  of  cork.  Three  glands  were 
touched  half  a dozen  times  with  a needle ; one  of  the  tentacles 
became  well  inflected  in  17  m., and  re-expanded  after  24  hrs.;  the 
two  others  never  moved.  The  homogeneous  fluid  within  the  cells 
of  the  tentacles  undergoes  aggregation  after  these  have  become 
inflected ; especially  if  given  a solution  of  carbonate  of  ammonia ; 
and  I observed  the  usual  movements  in  the  masses  of  proto- 
plasm. In  one  case,  aggregation  ensued  in  1 hr.  10  m.  after  a 
tentacle  had  carried  a bit  of  meat  to  the  centre.  From  these 
facts  it  is  clear  that  the  tentacles  of  Drosera  anglira  behave  like 
those  of  Drosera  rotundifolia. 

If  an  insect  is  placed  on  the  central  glands,  or  has  been 
naturally  caught  there,  the  apex  of  the  leaf  curls  inwards. 
For  instance,  dead  flies  were  placed  on  three  leaves  near  their 
bases,  and  after  24  hrs.  the  previously  straight  apices  were  curled 
completely  over,  so  as  to  embrace  and  conceal  the  flies;  they  had 
therefore  moved  through  an  angle  of  180°.  After  three  days  the 
apex  of  one  leaf,  together  with  the  tentacles,  began  to  re-expand. 
But  as  far  as  I have  seen — and  I made  many  trials — the  sides  of 
the  leaf  are  never  inflected,  and  this  is  the  one  functional  differ- 
ence between  this  species  and  Drosera  rotundifolia, 

Drosera  intermedia  (Hayne). — This  species  is  quite  as  common 
in  some  parts  of  England  as  Drosera  rotundifolia.  It  differs  from 
Drosera  anglica,  as  far  as  the  leaves  are  concerned,  only  in  their 
smaller  size,  and  in  their  tips  being  generally  a little  reflexed. 
They  capture  a large  number  of  insects.  The  tentacles  are  excited 
into  movement  by  all  the  causes  above  specified ; and  aggregation 
ensues,  with  movement  of  the  protoplasmic  masses.  I have  seen, 
through  a lens,  a tentacle  beginning  to  bend  in  less  than  a 
minute  after  a particle  of  raw  meat  had  been  placed  on  the 
gljind.  The  apex  of  the  leaf  curls  over  an  exciting  object  as  in 
the  case  of  Drosera  anylica.  Acid  secretion  is  copiously  poured 
over  captured  insects.  A leaf  which  had  embraced  a fly  with 
all  its  tentacles  re-expanded  after  nearly  three  days. 

Drosera  capensis. — This  species,  a native  of  the  Cape  of  Good 
Hope,  was  sent  to  me  by  Dr.  Hooker.  The  leaves  are  elongated, 
slightly  concave  along  the  middle  and  taper  towards  the  apex, 
18 


280 


DEOSERA  SPATHULATA. 


Chap.  XIL 


which  is  bluntly  pointed  and  reflexed.  They  rise  from  an  almost 
woody  axis,  and  their  greatest  peculiarity  consists  in  their 
foliaceous  green  footstalks,  wnich  are  almost  as  broad  and  even 
longer  than  the  gland-bearing  blade.  This  species,  therefore, 
probably  draws  more  nourishment  from  the  air,  and  less  from 
captured  insects,  than  the  other  species  of  the  genus.  Never- 
theless, the  tentacles  are  crowded  together  on  the  disc,  and  are 
extremely  numerous ; those  on  the  margins  being  much  longer 
than  the  central  ones.  All  the  glands  have  the  same  form ; their 
secretion  is  extremely  viscid  and  acid. 

The  specimen  which  I examined  had  only  just  recovered  from 
a weak  state  of  health.  This  may  account  for  the  tentacles 
moving  very  slowly  when  particles  of  meat  were  placed  on  the 
glands,  and  perhaps  for  my  never  succeedicg  in  causing  any 
movement  by  repeatedly  touching  them  with  a needle.  But 
with  all  the  species  of  the  genus  this  latter  stimulus  is  the  least 
effective  of  any.  Particles  of  glass,  cork,  and  coal-cinders,  were 
placed  on  the  glands  of  six  tentacles ; and  one  alone  moved  after 
an  interval  of  2 hrs.  30  m.  Nevertheless,  two  glands  were  ex- 
tremely sensitive  to  very  small  doses  of  the  nitrate  of  ammonia, 
namely  to  about  ^ of  a minim  of  a solution  (one  part  to  5250 
of  water),  containing  only  ^ grain  (*000562  mg.)  of 

the  salt.  Fragments  of  flies  were  placed  on  two  leaves  near  their 
tips,  which  became  incurved  in  15  hrs.  A fly  was  also  placed  in 
the  middle  of  the  leaf ; in  a few  hours  the  tentacles  on  each  side 
embraced  it,  and  in  8 hrs.  the  whole  leaf  directly  beneath  the 
fly  was  a little  bent  transversely.  By  the  next  morning,  after 
23  hrs.,  the  leaf  was  curled  so  completely  over  that  the  apex 
rested  on  the  upper  end  of  the  footstalk.  In  no  case  did  the 
sides  of  the  leaves  become  inflected.  A crushed  fly  was  placed 
on  the  foliaceous  footstalk,  but  produced  no  effect. 

Drosera  spathulata  (sent  to  me  by  Dr.  Hooker). — I made  only  a 
few  observations  on  this  Australian  species,  which  has  long, 
narrow  leaves,  gradually  widening  towards  their  tips.  The 
glands  of  the  extreme  marginal  tentacles  are  elongated  and  differ 
from  the  others,  as  in  the  case  of  Drosera  rotundifolia,  A fly  was 
placed  on  a leaf,  and  in  18  hrs.  it  was  embraced  by  the  adjoining 
tentacles.  Gum-water  dropped  on  several  leaves  produced  no 
effect.  A fragment  of  a leaf  was  immersed  in  a few  drops  of  a 
solution  of  one  part  of  carbonate  of  ammonia  to  146  of  water ; 
all  the  glands  were  instantly  blackened ; the  process  of  aggrega- 
tion could  be  seen  travelling  rapidly  down  the  cells  of  the  ten- 
tacles ; and  the  granules  of  protoplasm  soon  united  into  spheres 
and  variously  shaped  masses,  which  displayed  the  usual  move- 


Chap.  XIL 


DROSERA  FILIFORMIS. 


281 


ments.  Half  a minim  of  a solution  of  one  part  of  nitrate  of 
ammonia  to  146  of  water  was  next  placed  on  the  centre  of  a leaf ; 
after  6 hrs.  some  marginal  tentacles  on  both  sides  were  inflected, 
and  after  9 hrs.  they  met  in  the  centre.  The  lateral  edges  of  the 
leaf  also  became  incurved,  so  that  it  formed  a half-cylinder ; but 
the  apex  of  the  leaf  in  none  of  my  few  trials  was  inflected.  The 
above  dose  of  the  nitrate  (viz.  of  a grain,  or  *202  mg.)  was  too 
powerful,  for  in  the  course  of  23  hrs.  the  leaf  died. 

Drosera  filiformis, — This  North  American  species  grows  in 
such  abundance  in  parts  of  New  Jersey  as  almost  to  cover  the 
ground.  It  catches,  according  to  Mrs.  Treat,*  an  extraordinary 
number  of  small  and  large  insects,— even  great  flies  of  the 
genus  Asilus,  moths,  and  butterflies.  The  specimen  which  I 
examined,  sent  me  by  Dr.  Hooker,  had  thread-like  leaves,  from 
6 to  12  inches  in  length,  with  the  upper  surface  convex  and 
the  lower  flat  and  slightly  channelled.  The  whole  convex 
surface,  down  to  the  roots — for  there  is  no  distinct  footstalk — is 
covered  with  short  gland-bearing  tentacles,  those  on  the  margins 
being  the  longest  and  reflexed.  Bits  of  meat  placed  on  the 
glands  of  some  tentacles  caused  them  to  be  slightly  inflected  in 
20  m. ; but  the  plant  was  not  in  a vigorous  state.  After  6 hrs. 
they  moved  through  an  angle  of  90°,  and  in  24  hrs.  reached 
the  centre.  The  surrounding  tentacles  by  this  time  began  to 
curve  inwards.  Ultimately  a large  drop  of  extremely  viscid, 
slightly  acid  secretion  was  poured  over  the  meat  from  the 
united  glands.  Several  other  glands  were  touched  with  a little 
saliva,  and  the  tentacles  became  incurved  in  under  1 hr.,  and 
re-expanded  after  18  hrs.  Particles  of  glass,  cork,  cinders, 
thread,  and  gold-leaf,  were  placed  on  numerous  glands  on  two 
leaves ; in  about  1 hr.  four  tentacles  became  curved,  and  four 
others  after  an  additional  interval  of  2 hrs.  30  m.  I never  once 
succeeded  in  causing  any  movement  by  repeatedly  touching  the 
glands  with  a needle ; and  Mrs.  Treat  made  similar  trials  for  me 
with  no  success.  Small  flies  were  placed  on  several  leaves  near 
their  tips,  but  the  thread-like  blade  became  only  on  one  occasion 
very  slightly  bent,  directly  beneath  the  insect.  Perhaps  this 
indicates  that  the  blades  of  vigorous  plants  would  bend  over 
captured  insects,  and  Dr.  Canby  informs  me  that  this  is  the 
case ; but  the  movement  cannot  be  strongly  pronounced,  as  it 
was  not  observed  by  Mrs.  Treat. 

Drosera  hinata  (or  dicliotomd). — I am  much  indebted  to  Lady 


* ‘ American  Naturalist,*  Dec.  1873,  p.  705. 


282 


DROSERA  BINATA. 


Chap.  XII. 


Dorothy  Nevill  for  a fine  plant  of  this  almost  gigantic  Australian 
species,  which  differs  in  some  interesting  points  from  those  pre- 
viously described.  In  this  specimen  the  rush-like  footstalks  of 
the  leaves  were  20  inches  in  length.  The  blade  bifurcates  at  its 
junction  with  the  footstalk,  and  twice  or  thrice  afterwards,  curl- 
ing about  in  an  irregular  manner.  It  is  narrow,  being  only  2% 
of  an  inch  in  breadth.  One  blade  was  inches  long,  so  that 
the  entire  leaf,  including  the  footstalk,  was  above  27  inches  in 
length.  Both  surfaces  are  slightly  hollowed  out.  The  upper 
surface  is  covered  with  tentacles  arranged  in  alternate  rows; 
those  in  the  middle  being  short  and  crowded  together,  those 
towards  the  margins  longer,  even  twice  or  thrice  as  long  as  the 
blade  is  broad.  The  glands  of  the  exterior  tentacles  are  of  a 
much  darker  red  than  those  of  the  central  ones.  The  pedicels 
of  all  are  green.  The  apex  of  the  blade  is  attenuated,  and  bears 
very  long  tentacles.  Mr.  Copland  informs  me  that  the  leaves  of 
a plant  which  he  kept  for  some  years  were  generally  covered 
with  captured  insects  before  they  withered. 

The  leaves  do  not  differ  in  essential  points  of  structure  or  of 
function  from  those  of  the  previously  described  species.  Bits  of 
meat  or  a little  saliva  placed  on  the  glands  of  the  exterior 
tentacles  caused  well-marked  movement  in  3 m.,  and  -particles 
of  glass  acted  in  4 m.  The  tentacles  with  the  latter  particles 
re-expanded  after  22  hrs.  A piece  of  leaf  immersed  in  a few 
drops  of  a solution  of  one  part  of  carbonate  of  ammonia  to  437 
of  water  had  all  the  glands  blackened  and  all  the  tentacles 
inflected  in  5 m.  A bit  of  raw  meat,  placed  on  several  glands  in 
the  medial  furrow,  was  well  clasped  in  2 hrs.  10  m.  by  the  mar- 
ginal tentacles  on  both  sides.  Bits  of  roast  meat  and  small  flies 
did  not  act  quite  so  quickly ; and  albumen  and  fibrin  still  less 
quickly.  One  of  the  bits  of  meat  excited  so  much  secretion 
(which  is  always  acid)  that  it  flowed  some  way  down  the  medial 
furrow,  causing  the  inflection  of  the  tentacles  on  both  sides  as 
far  as  it  extended.  Particles  of  glass  placed  on  the  glands  in  the 
medial  furrow  did  not  stimulate  them  sufficiently  for  any  motor 
impulse  to  be  sent  to  the  outer  tentacles.  In  no  case  was  the 
blade  of  the  leaf,  even  the  attenuated  apex,  at  all  inflected. 

On  both  the  upper  and  lower  surface  of  tlie  blade  there  are 
numerous  minute,  almost  sessile  glands,  consisting  of  four,  eight, 
or  twelve  cells.  On  the  lower  surface  they  are  pale  purple,  on 
the  upper  greenish.  Nearly  similar  organs  occur  on  the  foot- 
stalks, but  they  are  smaller  and  often  in  a shrivelled  condition. 
The  minute  glands  on  the  blade  can  absorb  rapidly:  thus,  a 
piece  of  leaf  was  immersed  in  a solution  of  one  part  of  carbonate 


Chap.  Xli. 


DKOSEKA  BINATA. 


283 


of  ammonia  to  218  of  water  (1  gr.  to  2 oz.),  and  in  5 m.  they 
were  all  so  much  darkened  as  to  be  almost  black,  with  their 
contents  aggregated.  They  do  not,  as  far  as  I could  observe, 
secrete  spontaneously;  but  in  between  2 and  3 hrs.  after  a 
leaf  had  been  rubbed  with  a bit  of  raw  meat  moistened  with 
saliva,  they  seemed  to  be  secreting  freely ; and  this  conclusion 
was  afterwards  supported  by  other  appearances.  They  are, 
therefore,  homologous  with  the  sessile  glands  hereafter  to  be 
described  on  the  leaves  of  DionaBa  and  Drosophyllum.  In 
this  latter  genus  they  are  associated,  as  in  the  present  case,  with 
glands  which  secrete  spontaneously,  that  is,  without  being 
excited. 

Drosera  hinata  presents  another  and  more  remarkable  pecu- 
liarity, namely,  the  presence  of  a few  tentacles  on  the  backs  of 
the  leaves,  near  their  margins.  These  are  perfect  in  structure ; 
spiral  vessels  run  up  their  pedicels;  their  glands  are  sur- 
rounded by  drops  of  viscid  secretion,  and  they  have  the  power  of 
absorbing.  This  latter  fact  was  shown  by  the  glands  imme- 
diately becoming  black,  and  the  protoplasm  aggregated,  when 
a leaf  was  placed  in  a little  solution  of  one  part  of  carbonate 
of  ammonia  to  437  of  water.  These  dorsal  tentacles  are  short, 
not  being  nearly  so  long  as  the  marginal  ones  on  the  upper 
surface ; some  of  them  are  so  short  as  almost  to  graduate  into 
the  minute  sessile  glands.  Their  presence,  number,  and  size, 
vary  on  different  leaves,  and  they  are  arranged  rather  irre- 
gularly. On  the  back  of  one  leaf  I counted  as  many  as  twenty- 
one  along  one  side. 

These  dorsal  tentacles  differ  in  one  important  respect  from 
those  on  the  upper  surface,  namely,  in  not  possessing  any  power 
of  movement,  in  whatever  manner  they  may  be  stimulated.  Thus, 
portions  of  four  leaves  were  placed  at  different  times  in  solutions 
of  carbonate  of  ammonia  (one  part  to  437  or  218  of  water),  and 
all  the  tentacles  on  the  upper  surface  soon  became  closely 
inflected ; but  the  dorsal  ones  did  not  move,  though  the  leaves 
were  left  in  the  solution  for  many  hours,  and  though  their 
glands  from  their  blackened  colour  had  obviously  absorbed  some 
of  the  salt.  Eather  young  leaves  should  be  selected  for  such 
trials,  for  the  dorsal  tentacles,  as  they  grow  old  and  begin  to 
wither,  often  spontaneously  incline  towards  the  middle  of  the 
leaf.  If  these  tentacles  had  possessed  the  power  of  movement, 
they  would  not  have  been  thus  rendered  more  serviceable  to  the 
plant ; for  they  are  not  long  enough  to  bend  round  the  margin 
of  the  leaf  so  as  to  reach  an  insect  caught  on  the  upper  surface, 
Nor  would  it  have  been  of  any  use  if  these  tentacles  could  have 


284 


CONCLUDING  REMARKS. 


Chap.  XJI 


moved  towards  the  middle  of  the  lower  surface,  for  there  aro 
no  viscid  glands  there  by  which  insects  can  be  caught. 
Although  they  have  no  power  of  movement,  they  are  probably 
of  some  use  by  absorbing  animal  matter  from  any  minute  insect 
which  may  be  caught  by  them,  and  by  absorbing  ammonia  from 
the  rain-water.  But  their  varying  presence  and  size,  and  their 
irregular  position,  indicate  that  they  are  not  of  much  service, 
and  that  they  are  tending  towards  abortion.  In  a future  chap- 
ter we  shall  see  that  Drosophyllum,  with  its  elongated  leaves, 
probably  represents  the  condition  of  an  early  progenitor  of  the 
genus  Drosera;  and  none  of  the  tentacles  of  Drosophyllum,  neither 
those  on  the  upper  nor  lower  surface  of  the  leaves,  are  capable  of 
movement  when  excited,  though  they  capture  numerous  insects, 
which  serve  as  nutriment.  Therefore  it  seems  that  Drosera 
hinata  has  retained  remnants  of  certain  ancestral  characters — 
namely  a few  motionless  tentacles  on  the  backs  of  the  leaves, 
and  fairly  well  developed  sessile  glands — which  have  been  lost  by 
most  or  all  of  the  other  species  of  the  genus. 

Concluding  Bemarlcs, — From  what  we  have  now  seen, 
there  can  be  little  doubt  that  most  or  probably  all  the 
species  of  Drosera  are  adapted  for  catching  insects  by 
nearly  the  same  means.  Besides  the  two  Australian 
species  above  described,  it  is  said*  that  two  other 
species  from  this  country,  namely  Drosera  pallida  and 
Drosera  sulphurea,  close  their  leaves  upon  insects  with 
great  rapidity : and  the  same  phenomenon  is  mani- 
fested  by  an  Indian  species,  D.  lunata,  and  by  several 
of  those  of  the  Cape  of  Good  Hope,  especially  by 
“jD.  trinervis.^^  Another  Australian  species,  Drosera 
heterophylla  (made  by  Bindley  into  a distinct  genus, 
Sondera)  is  remarkable  from  its  peculiarly  shaped 
leaves,  but  I know  nothing  of  its  power  of  catching 
insects,  for  I have  seen  only  dried  specimens.  The 
leaves  form  minute  flattened  cups,  with  the  footstalks 
attached  not  to  one  margin,  but  to  the  bottom.  The 


* ‘ Gardener’s  Chronicle,’  1874,  p.  209. 


Chap.  XII. 


CONCLUDING  REMARKS. 


285 


inner  surface  and  the  edges  of  the  cups  are  studded 
with  tentacles,  which  include  fibro-vascular  bundles, 
rather  dilferent  from  those  seen  by  me  in  any  other 
species ; for  some  of  the  vessels  are  barred  and  punc- 
tured, instead  of  being  spiral.  The  glands  secrete 
copiously,  judging  from  the  quantity  of  dried  secretion 
adhering  to  them. 


286 


DION^A  MUSCirULA. 


Chap.  XIIL 


CHAPTER  XIII. 

DiONiEA  MLSCirULA. 

Structure  of  the  leaves  — Sensitiveness  of  the  filaments  — Eapid 
movement  of  the  lobes  caused  by  irritation  of  the  filaments  — 
Glands,  their  power  of  secretion  — Slow  movement  caused  by  the 
absorption  of  animal  matter  — Evidence  of  absorption  from  the 
aggregated  condition  of  the  glands  — Digestive  power  of  the  secre- 
tion— Action  of  chloroform,  ether,  and  hydrocyanic  acid  — The 
manner  in  which  insects  are  captured  — Use  of  the  marginal 
spikes — Kinds  of  insects  captured — The  transmission  of  the  motor 
impulse  and  mechanism  of  the  movements  — Ke-expansion  of  the 
lobes. 

This  plant,  commonly  called  Venus^  fly-trap,  from  the 
rapidity  and  force  of  its  movements,  is  one  of  the  most 
wonderful  in  the  world.*  It  is  a member  of  the 
small  family  of  the  Droseracea3,  and  is  found  only  in 
the  eastern  part  of  North  Carolina,  growing  in  damp 
situations.  The  roots  are  small ; those  of  a mo- 
derately fine  plant  which  I examined  consisted  of  two 
branches  about  1 inch  in  length,  springing  from  a 
bulbous  enlargement.  They  probably  serve,  as  in  the 
case  of  Drosera,  solely  for  the  absorption  of  w^ater; 
for  a gardener,  who  has  been  very  successful  in  the 
cultivation  of  this  plant,  grows  it,  like  an  epiphytic 
orchid,  in  well-drained  damp  moss  without  any  soil.f 
The  form  of  the  bilobed  leaf,  with  its  foliaceous  foot- 
stalk, is  shown  in  the  accompanying  drawing  (fig.  12). 


* Dr.  Hooker,  in  bis  address  to 
the  British  Association  at  Belfast, 
1874,  has  given  so  full  an  histori- 
cal account  of  the  observations 
which  have  been  published  on 


the  habits  of  this  plant,  that  it 
would  be  superfluous  on  my  part 
to  repeat  them. 

t ‘ Gardener’s  Chronicle,’  1874, 
p.  464. 


Chap.  XUI.  SENSITIVENESS  GF  FILAMENTS. 


289 


possible  to  touch  them  ever  so  lightly  or  quickly 
with  any  hard  object  without  causing  the  lobes  to 
close.  A piece  of  very  delicate  human  hair,  inches 
in  length,  held  dangling  over  a filament,  and  swayed 
to  and  fro  so  as  to  touch  it,  did  not  excite  any  move- 
ment. But  when  a rather  thick  cotton  thread  of  the 
same  length  was  similarly  swayed,  the  lobes  closed. 
Pinches  of  fine  wheaten  flour,  dropped  from  a height, 
produced  no  effect.  The  above-mentioned  hair  was 
then  fixed  into  a handle,  and  cut  off  so  that  1 inch 
projected ; this  length  being  sufficiently  rigid  to  sup- 
port itself  in  a nearly  horizontal  line.  The  extremity 
was  then  brought  by  a slow  movement  laterally  into 
contact  with  the  tip  of  a filament,  and  the  leaf  instantly 
closed.  On  another  occasion  two  or  three  touches  of 
the  same  kind  were  necessary  before  any  movement 
ensued.  When  we  consider  how  flexible  a fine  hair 
is,  we  may  form  some  idea  how  slight  must  be  the 
touch  given  by  the  extremity  of  a piece,  1 inch  in 
length,  moved  slowly. 

Although  these  filaments  are  so  sensitive  to  a momen- 
tary and  delicate  touch,  they  are  far  less  sensitive  than 
the  glands  of  Drosera  to  prolonged  pressure.  Several 
times  I succeeded  in  placing  on  the  tip  of  a filament, 
by  the  aid  of  a needle  moved  with  extreme  slowness, 
bits  of  rather  thick  human  hair,  and  these  did  not 
excite  movement,  although  they  were  more  than  ten 
times  as  long  as  those  which  caused  the  tentacles  of 
Drosera  to  bend ; and  although  in  this  latter  case  they 
were  largely  supported  by  the  dense  secretion.  On 
the  other  hand,  the  glands  of  Drosera  may  be  struck 
with  a needle  or  any  hard  object,  once,  twice,  or  even 
thrice,  with  considerable  force,  and  no  movement 
ensues.  This  singular  difference  in  the  nature  of 
the  sensitiveness  of  the  filaments  of  Dionaea  and  of 


290 


DION.EA  MUSCIPULA. 


Chap.  XIIL 


the  glands  of  Drosera  evidently  stands  in  relation  to 
the  habits  of  the  two  plants.  If  a minute  insect  alights 
with  its  delicate  feet  on  the  glands  of  Drosera,  it  is 
caught  by  the  viscid  secretion,  and  the  slight,  though 
prolonged  pressure,  gives  notice  of  the  presence  of 
prey,  which  is  secured  by  the  slow  bending  of  the 
tentacles.  On  the  other  hand,  the  sensitive  filaments 
of  Diona3a  are  not  viscid,  and  the  capture  of  insects 
can  be  assured  only  by  their  sensitiveness  to  a 
momentary  touch,  followed  by  the  rapid  closure  of 
the  lobes. 

As  just  stated,  the  filaments  are  not  glandular,  and 
do  not  secrete.  Nor  have  they  the  power  of  absorption, 
as  may  be  inferred  from  drops  of  a solution  of  car- 
bonate of  ammonia  (one  part  to  146  of  water),  placed 
on  two  filaments,  not  producing  any  effect  on  the 
contents  of  their  cells,  nor  causing  the  lobes  to  close. 
When,  however,  a small  portion  of  a leaf  with  an 
attached  filament  was  cut  off  and  immersed  in  the  same 
solution,  the  fluid  within  the  basal  cells  became  almost 
instantly  aggregated  into  purplish  or  colourless,  irre- 
gularly shaped  masses  of  matter.  The  process  of 
aggregation  gradually  travelled  up  the  filaments  from 
cell  to  cell  to  their  extremities,  that  is  in  a reverse 
course  to  what  occurs  in  the  tentacles  of  Drosera  when 
their  glands  have  been  excited.  Several  other  fila- 
ments were  cut  off  close  to  their  bases,  and  left  for  1 hr. 
30  m.  in  a weaker  solution  of  one  part  of  the  carbonate 
to  of  water,  and  this  caused  aggregation  in  all 
the  cells,  commencing  as  before  at  the  bases  of  the 
filaments. 

Long  immersion  of  the  filaments  in  distilled  water 
likewise  causes  aggregation.  Nor  is  it  rare  to  find 
the  contents  of  a few  of  the  terminal  cells  in  a 
spontaneously  aggregated  condition.  The  aggregated 


w 

r Chap. 


Chap.  XIIL  SENSITIVENESS  OF  FILAMENTS. 

masses  undergo  incessant  slow  changes  of  form,  uniting 
and  again  separating;  and  some  of  them  apparently 
revolve  round  their  own  axes.  A current  of  colourless 
granular  protoplasm  could  also  be  seen  travelling 
round  the  walls  of  the  cells.  This  current  ceases  to 
be  visible  as  soon  as  the  contents  are  well  aggregated ; 
but  it  probably  still  continues,  though  no  longer 
visible,  owing  to  all  the  granules  in  the  flowing  layer 
having  become  united  with  the  central  masses.  In  all 
these  respects  the  filaments  of  Dionaea  behave  exactly 
like  the  tentacles  of  Drosera. 

Notwithstanding  this  similarity  there  is  one  re- 
markable difference.  The  tentacles  of  Drosera,  after 
their  glands  have  been  repeatedly  touched,  or  a particle 
of  any  kind  has  been  placed  on  them,  become  inflected 
and  strongly  aggregated.  No  such  effect  is  pro- 
duced by  touching  the  filaments  of  Dionaea ; I com- 
pared, after  an  hour  or  two,  some  which  had  been 
touched  and  some  which  had  not,  and  others  after 
twenty-five  hours,  and  there  was  no  difference  in  the 
contents  of  the  cells.  The  leaves  were  kept  open  all 
the  time  by  clips;  so  that  the  filaments  were  not 
pressed  against  the  opposite  lobe. 

Drops  of  water,  or  a thin  broken  stream,  falling 
from  a height  on  the  filaments,  did  not  cause  the 
des  to  close ; though  these  filaments  were  afterwards 
?)ved  to  be  highly  sensitive.  No  doubt,  as  in  the 
case  of  Drosera,  the  plant  is  indifferent  to  the  heaviest 
shower  of  rain.  Drops  of  a solution  of  a half  an  ounce 
of  sugar  to  a fluid  ounce  of  water  were  repeatedly 
allowed  to  fall  from  a height  on  the  filaments,  but 
produced  no  effect,  unless  they  adhered  to  them. 
Again,  I blew  many  times  through  a fine  pointed 
tube  with  my  utmost  force  against  the  filaments 
without  any  effect;  such  blowing  being  received 


292 


DION^A  MUSCIPULA. 


Chap.  Xm. 


with  as  much  indifference  as  no  doubt  is  a heavy  gale 
of  wind.  We  thus  see  that  the  sensitiveness  of  the 
filaments  is  of  a specialised  nature,  being  related  to  a 
momentary  touch  rather  than  to  prolonged  pressure ; 
and  the  touch  must  not  be  from  fluids,  such  as  air  or 
water,  but  from  some  solid  object. 

Although  drops  of  water  and  of  a moderately  strong 
solution  of  sugar,  falling  on  the  filaments,  does  not 
excite  them,  yet  the  immersion  of  a leaf  in  pure  water 
sometimes  caused  the  lobes  to  close.  One  leaf  was  left 
immersed  for  1 hr.  10  m.,  and  three  other  leaves  for 
some  minutes,  in  water  at  temperatures  varying  be- 
tween 59^^  and  65°  (15°  to  18°-3  Cent.)  without  any 
effect.  One,  however,  of  these  four  leaves,  on  being 
gently  withdrawn  from  the  water,  closed  rather 
quickly.  The  three  other  leaves  were  proved  to  be  in 
good  condition,  as  they  closed  when  their  filaments 
were  touched.  Nevertheless  two  fresh  leaves  on  being 
dipped  into  water  at  75°  and  62^°  (23°*8  and  16°*9 
Cent.)  instantly  closed.  These  were  then  placed  with 
their  footstalks  in  water,  and  after  23  hrs.  partially 
re-expanded;  on  touching  their  filaments  one  of 
them  closed.  This  latter  leaf  after  an  additional 
24  hrs.  again  re-expanded,  and  now,  on  the  filaments 
of  both  leaves  being  touched,  both  closed.  We  tlms 
see  that  a short  immersion  in  water  does  not  at  H 
injure  the  leaves,  but  sometimes  excites  the  lobes 
to  close.  The  movement  in  the  above  cases  was 
evidently  not  caused  by  the  temperature  of  the  water. 
It  has  been  shown  that  long  immersion  causes  the 
purple  fluid  within  the  cells  of  the  sensitive  filaments 
to  become  aggregated ; and  the  tentacles  of  Drosera 
are  acted  on  in  the  same  manner  by  long  immersion, 
often  being  somewhat  inflected.  In  both  cases  the 
result  is  probably  due  to  a slight  degree  of  exosmose. 


Thap.  XIII.  SENSITIVENESS  OF  FILAMENTS. 


293 


I am  confirmed  in  this  belief  by  the  effects  of 
immersing  a leaf  of  Dionsea  in  a moderately  strong 
solution  of  sugar  ; the  leaf  having  been  previously  left 
for  1 hr.  10  m.  in  water  without  any  effect ; for  now  the 
lobes  closed  rather  quickly,  the  tips  of  the  marginal 
spikes  crossing  in  2 m.  30  s.,  and  the  leaf  being  com- 
pletely shut  in  3 m.  Three  leaves  were  then  immersed 
in  a solution  of  half  an  ounce  of  sugar  to  a fluid 
ounce  of  water,  and  all  three  leaves  closed  quickly. 
As  I was  doubtful  whether  this  was  due  to  the  cells  on 
the  upper  surface  of  the  lobes,  or  to  the  sensitive  fila- 
ments, being  acted  on  by  exosmose,  one  leaf  was  first 
tried  by  pouring  a little  of  the  same  solution  in  the 
furrow  between  the  lobes  over  the  midrib,  which  is  the 
chief  seat  of  movement.  It  was  left  there  for  some  time, 
but  no  movement  ensued.  The  whole  upper  surface  of 
leaf  was  then  painted  (except  close  round  the  bases  of 
the  sensitive  filaments,  which  I could  not  do  without 
risk  of  touching  them)  with  the  same  solution,  but 
no  effect  was  produced.  So  that  the  cells  on  the  upper 
surface  are  not  thus  affected.  But  when,  after  many 
trials,  I succeeded  in  getting  a drop  of  the  solution  to 
cling  to  one  of  the  filaments,  the  leaf  quickly  closed. 
Hence  we  may,  I think,  conclude  that  the  solution 
causes  fluid  to  pass  out  of  the  delicate  cells  of  the 
filaments  by  exosmose ; and  that  this  sets  up  some 
molecular  change  in  their  contents,  analogous  to  that 
which  must  be  produced  by  a touch. 

The  immersion  of  leaves  in  a solution  of  sugar 
affects  them  for  a much  longer  time  than  does  an 
immersion  in  water,  or  a touch  on  the  filaments ; for  in 
these  latter  cases  the  lobes  begin  to  re-expand  in  less 
than  a day.  On  the  other  hand,  of  the  three  leaves 
which  were  immersed  for  a short  time  in  the  solution, 
and  were  then  washed  by  means  of  a syringe  inserted 


294 


DION^A  MUSCIPULA. 


Chap.  XI  IL 


between  the  lobes,  one  re-expanded  after  tw^'  days; 
a second  after  seven  days ; and  the  third  after  nine 
days.  The  leaf  which  closed,  owing  to  a drop  of  the 
solution  having  adhered  to  one  of  the  filaments, 
opened  after  two  days. 

I was  surprised  to  find  on  two  occasions  that  the 
heat  from  the  rays  of  the  sun,  concentrated  by  a lens 
on  the  bases  of  several  filaments,  so  that  they  were 
scorched  and  discoloured,  did  not  cause  any  move- 
ment ; though  the  leaves  were  active,  as  they  closed, 
though  rather  slowly,  when  a filament  on  the  opposite 
side  was  touched.  On  a third  trial,  a fresh  leaf  closed 
after  a time,  though  very  slowly ; the  rate  not  being 
increased  by  one  of  the  filaments,  which  had  not  been 
injured,  being  touched.  After  a day  these  three  leaves 
opened,  and  were  fairly  sensitive  when  the  uninjured 
filaments  were  touched.  The  sudden  immersion  of  a 
leaf  into  boiling  water  does  not  cause  it  to  close. 
Judging  from  the  analogy  of  Drosera,  the  heat  in 
these  several  cases  was  too  great  and  too  suddenly 
applied.  The  surface  of  the  blade  is  very  slightly 
sensitive ; it  may  be  freely  and  roughly  handled,  with- 
out any  movement  being  caused.  A leaf  was  scratched 
rather  hard  with  a needle,  but  did  not  close ; but  when 
the  triangular  space  between  the  three  filaments  on 
another  leaf  was  similarly  scratched,  the  lobes  closed. 
They  always  closed  when  the  blade  or  midrib  was 
deeply  pricked  or  cut.  Inorganic  bodies,  even  of  large 
size,  such  as  bits  of  stone,  glass,  &c. — or  organic  bodies 
not  containing  soluble  nitrogenous  matter,  such  as  bits 
of  wood,  cork,  moss,  — or  bodies  containing  soluble 
nitrogenous  matter,  if  perfectly  dry,  such  as  bits  of 
meat,  albumen,  gelatine,  &c.,  may  be  long  left  (and 
many  were  tried)  on  the  lobes,  and  no  movement  is 
excited.  The  result,  however,  is  widely  different,  as  we 


Chap. 


SECRETION  AND  ABSORPTION. 


295 


shall  presently  see,  if  nitrogenous  organic  bodies  which 
are  at  all  damp,  are  left  on  the  lobes ; for  these  then 
close  by  a slow  and  gradual  movement,  very  different 
from  that  caused  by  touching  one  of  the  sensitive  fila- 
ments. The  footstalk  is  not  in  the  least  sensitive ; 
a pin  may  be  driven  through  it,  or  it  may  be  cut  off. 
and  no  movement  follows. 

The  upper  surface  of  the  lobes,  as  already  stated, 
is  thickly  covered  with  small  purplish,  almost  sessile 
glands.  These  have  the  power  both  of  secretion 
and  absorption;  but  unlike  those  of  Drosera,  they 
do  not  secrete  until  excited  by  the  absorption  of 
nitrogenous  matter.  No  other  excitement,  as  far  as  I 
have  seen,  produces  this  effect.  Objects,  such  as  bits 
of  wood,  cork,  moss,  paper,  stone,  or  glass,  may  be  left 
for  a length  of  time  on  the  surface  of  a leaf,  and  it 
remains  quite  dry.  Nor  does  it  make  any  difference  if 
the  lobes  close  over  such  objects.  For  instance,  some 
little  balls  of  blotting  paper  were  placed  on  a leaf, 
and  a filament  was  touched ; and  when  after  24  hrs. 
the  lobes  began  to  re-open,  the  balls  were  removed  by 
the  aid  of  thin  pincers,  and  w^ere  found  perfectly  dry. 
On  the  other  hand,  if  a bit  of  damp  meat  or  a crushed 
fly  is  placed  on  the  surface  of  an  expanded  leaf,  the 
glands  after  a time  secrete  freely.  In  one  such  case 
there  was  a little  secretion  directly  beneath  the  meat 
in  4 hrs. ; and  after  an  additional  3 hrs.  there  was  a 
considerable  quantity  both  under  and  close  round  it. 
In  another  case,  after  3 hrs.  40  m.,  the  bit  of  meat  was 
quite  wet.  But  none  of  the  glands  secreted,  except- 
ing those  which  actually  touched  the  meat  or  the 
secretion  containing  dissolved  animal  matter. 

If,  however,  the  lobes  are  made  to  close  over  a bit  of 
meat  or  an  insect,  the  result  is  different,  for  the  glands 
over  the  whole  surface  of  the  leaf  now  secrete  copiously. 


296 


DION^A  MUSCIPULA. 


XIIL 

As  in  this  case  the  glands  on  both  sides  are  pressed 
against  the  meat  or  insect,  the  secretion  from  the  first 
is  twice  as  great  as  when  a bit  of  meat  is  laid  on  the 
surface  of  one  lobe ; and  as  the  two  lobes  come  into 
almost  close  contact,  the  secretion,  containing  dis- 
solved animal  matter,  spreads  by  capillary  attraction, 
causing  fresh  glands  on  both  sides  to  begin  secreting 
in  a continually  widening  circle.  The  secretion  is 
almost  colourless,  slightly  mucilaginous,  and,  judging 
by  the  manner  in  which  it  coloured  litmus  paper, 
more  strongly  acid  than  that  of  Drosera.  It  is  so 
copious  that  on  one  occasion,  when  a leaf  was  cut 
open,  on  which  a small  cube  - of  albumen  had  been 
placed  45  hrs.  before,  drops  rolled  off  the  leaf.  On 
another  occasion,  in  which  a leaf  with  an  enclosed  bit 
of  roast  meat  spontaneously  opened  after  eight  days, 
there  was  so  much  secretion  in  the  furrow  over  the 
midrib  that  it  trickled  down.  A large  crushed  fly 
(Tipula)  was  placed  on  a leaf  from  which  a small 
portion  at  the  base  of  one  lobe  had  previously  been 
cut  away,  so  that  an  opening  was  left ; and  through 
this,  the  secretion  continued  to  run  down  the  footstalk 
during  nine  days, — that  is,  for  as  long  a time  as  it  was 
observed.  By  forcing  up  one  of  the  lobes,  I was  able 
to  see  some  distance  between  them,  and  all  the  glands 
within  sight  were  secreting  freely. 

We  have  seen  that  inorganic  and  non-nitrogenous 
objects  placed  on  the  leaves  do  not  excite  any  move- 
ment ; but  nitrogenous  bodies,  if  in  the  least  degree 
damp,  cause  after  several  hours  the  lobes  to  close 
slowly.  Thus  bits  of  quite  dry  meat  and  gelatine  were 
placed  at  opposite  ends  of  the  same  leaf,  and  in  the 
course  of  24  hrs.  excited  neither  secretion  nor  move- 
ment. They  were  then  dipped  in  water,  their  sur- 
faces dried  on  blotting  paper,  and  replaced  on  the  same 


Chap.  XIII.  SECRETION  AND  ABSORPTION.  297 

leaf,  the  plant  being  now  covered  with  a bell-glass. 
After  24  hrs.  the  damp  meat  had  excited  some  acid 
secretion,  and  the  lobes  at  this  end  of  the  leaf  were 
almost  shut.  At  the  other  end,  where  the  damp  gela- 
tine lay,  the  leaf  was  still  quite  open,  nor  had  any 
secretion  been  excited ; so  that,  as  with  Drosera,  gela- 
tine is  not  nearly  so  exciting  a substance  as  meat. 
The  secretion  beneath  the  meat  was  tested  by  push- 
ing a strip  of  litmus  paper  under  it  (the  filaments  not 
being  touched),  and  this  slight  stimulus  caused  the 
leaf  to  shut.  On  the  eleventh  day  it  reopened ; but 
the  end  where  the  gelatine  lay,  expanded  several  hours 
before  the  opposite  end  with  the  meat. 

A second  bit  of  roast  meat,  which  appeared  dry, 
though  it  had  not  been  purposely  dried,  was  left  for 
24  hrs.  on  a leaf,  caused  neither  movement  nor  secre- 
tiqn.  The  plant  in  its  pot  was  now  covered  with  a 
bell-glass,  and  the  meat  absorbed  some  moisture  from 
the  air ; this  sufficed  to  excite  acid  secretion,  and  by 
the  next  morning  the  leaf  was  closely  shut.  A third 
bit  of  meat,  dried  so  as  to  be  quite  brittle,  was  placed 
on  a leaf  under  a bell-glass,  and  this  also  became  in 
24  hrs.  slightly  damp,  and  excited  some  acid  secretion, 
but  no  movement. 

A rather  large  piece  of  perfectly  dry  albumen  was 
left  at  one  end  of  a leaf  for  24  hrs.  without  any 
effect.  It  was  then  soaked  for  a few  minutes  in 
water,  rolled  about  on  blotting  paper,  and  replaced 
on  the  leaf;  in  9 hrs.  some  slightly  acid  secretion 
was  excited,  and  in  24  hrs.  this  end  of  the  leaf  was 
partially  closed.  The  bit  of  albumen,  which  was  now 
surrounded  by  much  secretion,  was  gently  removed, 
and  although  no  filament  was  touched,  the  lobes 
closed.  In  this  and  the  previous  case,  it  appears  that 
the  absorption  of  animal  matter  by  the  glands  renders 


298 


DION^A  MUSCIPULA. 


Chap.  Xm, 


the  surface  of  the  leaf  much  more  sensitive  to  a touch 
than  it  is  in  its  ordinary  state ; and  this  is  a curious 
fact.  Two  days  afterwards  the  end  of  the  leaf  where 
nothing  had  been  placed  began  to  open,  and  on  the 
third  day  was  much  more  open  than  the  opposite  end 
where  the  albumen  had  lain. 

Lastly,  large  drops  of  a solution  of  one  part  of  car- 
bonate of  ammonia  to  146  of  water  were  placed  on 
some  leaves,  but  no  immediate  movement  ensued.  I 
did  not  then  know  of  the  slow  movement  caused  by 
animal  matter,  otherwise  I should  have  observed  the 
leaves  for  a longer  time,  and  they  would  probably 
have  been  found  closed,  though  the  solution  (judging 
from  Drosera)  was,  perhaps,  too  strong. 

From  the  foregoing  cases  it  is  certain  that  bits  of 
meat  and  albumen,  if  at  all  damp,  excite  not  only  the 
glands  to  secrete,  but  the  lobes  to  close.  This  move- 
ment is  widely  different  from  the  rapid  closure  caused 
by  one  of  the  filaments  being  touched.  We  shall  see 
its  importance  when  we  treat  of  the  manner  in  which 
insects  are  captured.  There  is  a great  contrast  be- 
tween Drosera  and  Dionsea  in  the  effects  produced  by 
mechanical  irritation  on  the  one  hand,  and  the  absorp- 
tion of  animal  matter  on  the  other.  Particles  of  glass 
placed  on  the  glands  of  the  exterior  tentacles  of  Dro- 
sera excite  movement  within  nearly  the  same  time, 
as  do  particles  of  meat,  the  latter  being  rather  the 
most  efficient ; but  when  the  glands  of  the  disc  have 
bits  of  meat  given  them,  they  transmit  a motor  impulse 
to  the  exterior  tentacles  much  more  quickly  than  do 
these  glands  when  bearing  inorganic  particles,  or 
when  irritated  by  repeated  touches.  On  the  other 
hand,  with  Dionsea,  touching  the  filaments  excites 
incomparably  quicker  movement  than  the  absorption 
of  animal  matter  by  the  glands.  Nevertheless,  in 


CflAP.  XIII.  SECRETION  A.ND  ABSORPTION. 


299 


certain  cases,  this  latter  stimulus  is  the  more  powerful 
of  the  two.  On  three  occasions  leaves  were  found 
which  from  some  cause  were  torpid,  so  that  their  lobes 
closed  only  slightly,  however  much  their  filaments 
were  irritated ; but  on  inserting  crushed  insects 
between  the  lobes,  they  became  in  a day  closely  shut. 

The  facts  just  given  plainly  show  that  the  glands 
have  the  power  of  absorption,  for  otherwise  it  is  im- 
possible that  the  leaves  should  be  so  differently  af- 
fected by  non-nitrogenous  and  nitrogenous  bodies,  and 
between  these  latter  in  a dry  and  damp  condition.  It 
is  surprising  how  slightly  damp  a bit  of  meat  or  albu- 
men need  be  in  order  to  excite  secretion  and  afterwards 
slow  movement,  and  equally  surprising  how  minute  a 
quantity  of  animal  matter,  when  absorbed,  suffices  to 
produce  these  two  effects.  It  seems  hardly  credible, 
and  yet  it  is  certainly  a fact,  that  a bit  of  hard-boiled 
white  of  egg,  first  thoroughly  dried,  then  soaked 
for  some  minutes  in  water  and  rolled  on  blotting 
paper,  should  yield  in  a few  hours  enough  animal 
matter  to  the  glands  to  cause  them  to  secrete,  and 
afterwards  the  lobes  to  close.  That  the  glands  have 
the  power  of  absorption  is  likewise  shown  by  the  very 
different  lengths  of  time  (as  we  shall  presently  see) 
during  which  the  lobes  remain  closed  over  insects  and 
other  bodies  yielding  soluble  nitrogenous  matter,  and 
over  such  as  do  not  yield  any.  But  there  is  direct 
evidence  of  absorption  in  the  condition  of  the  glands 
which  have  remained  for  some  time  in  contact  with 
animal  matter.  Thus  bits  of  meat  and  crushed  insects 
were  several  times  placed  on  glands,  and  these  were 
compared  after  some  hours  with  other  glands  from 
distant  parts  of  the  same  leaf.  The  latter  showed 
not  a trace  of  aggregation,  whereas  those  which 
had  been  in  contact  with  the  animal  matter  were 


300 


DION^A  MUSCIPULA. 


Chat.  XIII. 


well  aggregated.  Aggregation  may  be  seen  to  occur 
very  quickly  if  a piece  of  a leaf  is  immersed  in 
a weak  solution  of  carbonate  of  ammonia.  Again, 
small  cubes  of  albumen  and  gelatine  were  left  for 
eight  days  on  a leaf,  which  was  then  cut  open.  The 
whole  surface  was  bathed  with  acid  secretion,  and 
every  cell  in  the  many  glands  which  were  examined 
had  its  contents  aggregated  in  a beautiful  manner 
into  dark  or  pale  purple,  or  colourless  globular 
masses  of  protoplasm.  These  underwent  incessant 
slow  changes  of  forms ; sometimes  separating  from 
one  another  and  then  reuniting,  exactly  as  in  the 
cells  of  Drosera.  Boiling  water  makes  the  contents 
of  the  gland-cells  white  and  opaque,  but  not  so 
purely  white  and  porcelain-like  as  in  the  case  of 
Drosera.  How  living  insects,  when  naturally  caught, 
excite  the  glands  to  secrete  so  quickly  as  they  do,  I 
know  not;  but  I suppose  that  the  great  pressure  to 
which  they  are  subjected  forces  a little  excretion 
from  either  extremity  of  their  bodies,  and  we  have 
seen  that  an  extremely  small  amount  of  nitrogenous 
matter  is  sufficient  to  excite  the  glands. 

Before  passing  on  to  the  subject  of  digestion,  I may 
state  that  I endeavoured  to  discover,  with  no  success, 
the  functions  of  the  minute  octofld  processes  with 
which  the  leaves  are  studded.  From  facts  hereafter  to 
be  given  in  the  chapters  on  Aldrovanda  and  Utricu- 
laria,  it  seemed  probable  that  they  served  to  absorb 
decayed  matter  left  by  the  captured  insects;  but 
their  position  on  the  backs  of  the  leaves  and  on  the 
footstalks  rendered  this  almost  impossible.  Never- 
theless, leaves  were  immersed  in  a solution  of  one  part 
of  urea  to  437  of  water,  and  after  24  hrs.  the  orange 
layer  of  protoplasm  within  the  arms  of  these  processes 
did  not  appear  more  aggregated  than  in  other  speci- 


CUAP.XIII. 


DIGESTION. 


301 


mens  kept  in  water.  I then  tried  suspending  a leaf 
in  a bottle  over  an  excessively  putrid  infusion  of 
raw  meat,  to  see  whether  they  absorbed  the  vapour, 
but  their  contents  were  not  affected. 

Digestive  Power  of  the  Secretion* — When  a leaf  closes 
over  any  object,  it  may  be  said  to  form  itself  into  a 
temporary  stomach ; and  if  the  object  yields  ever  so 
little  animal  matter,  this  serves,  to  use  Schiflf  s expres- 
sion, as  a peptogene,  and  the  glands  on  the  surface 
pour  forth  their  acid  secretion,  which  acts  like  the 
gastric  juice  of  animals.  As  so  many  experiments 
were  tried  on  the  digestive  power  of  Drosera,  only  a 
few  were  made  with  Dionaea,  but  they  were  amply 
sufficient  to  prove  that  it  digests.  This  plant,  more- 
over, is  not  so  well  fitted  as  Drosera  for  observation, 
as  the  process  goes  on  within  the  closed  lobes.  Insects, 
even  beetles,  after  being  subjected  to  the  secretion  for 
several  days,  are  surprisingly  softened,  though  their 
chitinous  coats  are  not  corroded. 


Expenment  1. — A cube  of  albumen  of  of  an  inch  (2*540 
mm.)  was  placed  at  one  end  of  a leaf,  and  at  the  other  end 
an  oblong  piece  of  gelatine,  \ of  an  inch  (5*08  mm.)  long,  and 


♦ Dr.  W.  M.  Canby,  of  V^il- 
mington,  to  whom  I am  much 
^ indebted  for  information  regard- 
ing Dionaea  in  its  native  home, 
has  published  in  the  ‘ Gardener’s 
Monthly,’  Philadelphia,  August 
1868,  some  interesting  observa- 
tions. He  ascertained  that  the 
secretion  digests  animal  matter, 
such  as  the  contents  of  insects, 
bits  of  meat,  &c. ; and  that  the 
secretion  is  reabsorbed.  He  was 
also  well  aware  that  the  lobes 
remain  closed  for  a much  longer 
time  when  in  contact  with  animal 
matter  than  when  made  to  shut 
by  a mere  touch,  or  over  objects 


not  yielding  soluble  nutriment; 
and  that  in  these  latter  cases  the 
glands  do  not  secrete.  The  Eev. 
Dr.  Curtis  first  observed  (‘  Boston 
Journal  Nat.  Hist.’  vol.  i.  p.  123) 
the  secretion  from  the  glands.  I 
may  here  add  that  a gardener, 
Mr.  Knight,  is  said  (Kirby  and 
Spencer’s  ‘Introduction  to  Ento- 
mology,’ 1818,  vol.  i.  p.  295)  to 
have  found  that  a plant  of  the 
Dionaea,  on  the  leaves  of  which 
“he  laid  fine  filaments  of  raw 
beef,  was  much  more  luxuriant 
in  its  growth  than  others  not  so 
treated.” 


302 


DION^A.  MUSCIPULA. 


Chap.  XIIL 


broad;  the  leaf  was  then  made  to  close.  It  was  cut  open 
after  45  hrs.  The  albumen  was  hard  and  compressed,  with 
its  angles  only  a little  rounded ; the  gelatine  was  corroded  into 
an  oval  form ; and  both  were  bathed  in  so  much  acid  secretion 
that  it  di’opped  off  the  leaf.  The  digestive  process  apparently 
is  rather  slower  than  in  Drosera,  and  this  agrees  with  the  length 
of  time  during  which  the  leaves  remain  closed  over  digestible 
objects. 

Experiment  2. — A bit  of  albumen  of  an  inch  square,  but 
only  2^  in  thickness,  and  a piece  of  gelatine  of  the  same  size  as 
before,  were  placed  on  a leaf,  which  eight  days  afterwards  was 
cut  open.  The  surface  was  bathed  with  slightly  adhesive,  very 
acid  secretion,  and  the  glands  were  all  in  an  aggregated  condi- 
tion. Not  a vestige  of  the  albumen  or  gelatine  was  left.  Simi- 
larly sized  pieces  were  placed  at  the  same  time  on  wet  moss  on 
the  same  pot,  so  that  they  were  subjected  to  nearly  similar  con- 
ditions ; after  eight  days  these  were  brown,  decayed,  and  matted 
with  fibres  of  mould,  but  had  not  disappeared. 

Experiment  3. — A piece  of  albumen  of  an  inch  (3*81  mm.; 
long,  and  broad  and  thick,  and  a piece  of  gelatine  of  the 
same  size  as  before,  were  placed  on  another  leaf,  which  was  cut 
open  after  seven  days;  not  a vestige  of  either  substance  was 
left,  and  only  a moderate  amount  of  secretion  on  the  surface. 

Experiment  4. — Pieces  of  albumen  and  gelatine,  of  the  same 
size  as  in  the  last  experiment,  were  placed  on  a leaf,  which 
spontaneously  opened  after  twelve  days,  and  here  again  not  a 
vestige  of  either  was  left,  and  only  a little  secretion  at  one  end 
of  the  midrib. 

Experiment  5. — Pieces  of  albumen  and  gelatine  of  the  same 
size  were  placed  on  another  leaf,  which  after  twelve  days  was 
still  firmly  closed,  but  had  begun  to  wither;  it  was  cut  open, 
and  contained  nothing  except  a vestige  of  brown  matter  where 
the  albumen  had  lain.  . , 

Experiment  6. — A cube  of  albumen  of  of  an  inch  and  a 
piece  of  gelatine  of  the  same  size  as  before  were  placed  on  a 
leaf,  which  opened  spontaneously  after  thirteen  days.  The 
albumen,  which  was  twice  as  thick  as  in  the  latter  experiments, 
was  too  large ; for  the  glands  in  contact  with  it  were  injured 
and  were  dropping  off;  a film  also  of  albumen  of  a brown 
colour,  matted  with  mould,  was  left.  All  the  gelatine  was 
absorbed,  and  there  was  only  a little  acid  secretion  left  on 
the  midrib. 

Experiment  7. — A bit  of  half  roasted  meat  (not  measured)  and 
a bit  of  gelatine  were  placed  on  the  two  ends  of  a leaf,  which 


Chap.  Xni. 


DIGESTION. 


303 


opened  spontaneously  after  eleven  days ; a vestige  of  the  meat 
was  left,  and  the  surface  of  the  leaf  was  here  blackened;  the 
gelatine  had  all  disappeared. 

Experiment  8.— A bit  of  half  roasted  meat  (not  measured) 
was  placed  on  a leaf  which  was  forcibly  kept  open  by  a clip,  so 
that  it  was  moistened  with  the  secretion  (very  acid)  only  on  its 
lower  surface.  Nevertheless,  after  only  22^  hrs.  it  was  sur- 
prisingly softened,  when  compared  with  another  bit  of  the 
same  meat  which  had  been  kept  damp. 

Experiment  9. — A cube  of  compact 

roasted  beef  was  placed  on  a leaf,  which  opened  spontaneously 
after  twelve  days ; so  much  feebly  acid  secretion  was  left  on  the 
leaf  that  it  trickled  off.  The  meat  was  completely  disintegrated, 
but  not  all  dissolved ; there  was  no  mould.  The  little  mass  was 
placed  under  the  microscope ; some  of  the  fibrillae  in  the  middle 
still  exhibited  transverse  striae;  others  showed  not  a vestige 
of  striae ; and  eyery  gradation  could  be  traced  between  these 
two  states.  Globules,  apparently  of  fat,  and  some  undigested 
fibro-elastic  tissue  remained.  The  meat  was  thus  in  the 
same  state  as  that  formerly  described,  which  was  half  di- 
gested by  Drosera.  Here,  again,  as  in  the  case  of  albumen, 
the  digestive  process  seems  slower  than  in  Drosera.  At  the 
opposite  end  of  the  same  leaf,  a firmly  compressed  pellet  of 
bread  had  been  placed;  this  was  completely  disintegrated,  I 
suppose,  owing  to  the  digestion  of  the  gluten,  but  seemed  very 
little  reduced  in  bulk. 

Experiment  10.  — A cube  of  ^ of  an  inch  of  cheese  and 
another  of  albumen  were  placed  at  opposite  ends  of  the  same 
leaf.  After  nine  days  the  lobes  opened  spontaneously  a little 
at  the  end  enclosing  the  cheese,  but  hardly  any  or  none  was 
dissolved,  though  it  was  softened  and  surrounded  by  secre- 
tion. Two  days  subsequently  the  end  with  the  albumen  also 
opened  spontaneously  (i.e.  eleven  days  after  it  was  put  on),  a 
mere  trace  in  a blackened  and  dry  condition  being  left. 

Experiment  11. — The  same  experiment  with  cheese  and  albu- 
men repeated  on  another  and  rather  torpid  leaf.  The  lobes  at  the 
end  with  the  cheese,  after  an  interval  of  six  days,  opened  spon- 
taneously a little;  the  cube  of  cheese  was  much  softened,  but 
not  dissolved,  and  but  little,  if  at  all,  reduced  in  size.  Twelve 
hours  afterwards  the  end  with  the  albumen  opened,  which 
now  consisted  of  a large  drop  of  transparent,  not  acid,  viscid 
fluid. 

Experiment  12. — Same  experiment  as  the  two  last,  and  here 
again  the  leaf  at  the  end  enclosing  the  cheese  opened  before  the 
14 


304 


DIONiEA  MUSCIPULA. 


Chap.  XIII 


opposite  end  with  the  albumen ; but  no  further  observations 
were  made. 

Experiment  13. — A globule  of  chemically  prepared  casein, 
about  Jq  of  an  inch  in  diameter,  was  placed  on  a leaf,  which 
spontaneously  opened  after  eight  days.  The  casein  now  con- 
sisted of  a soft  sticky  mass,  very  little,  if  at  all,  reduced  in  size, 
but  bathed  in  acid  secretion. 

These  experiments  are  sufficient  to  show  that  the 
secretion  from  the  glands  of  Dionaea  dissolves  albu- 
men, gelatine,  and  meat,  if  too  large  pieces  are 
not  given.  Globules  of  fat  and  fibro-elastic  tissue 
are  not  digested.  The  secretion,  with  its  dissolved 
matter,  if  not  in  excess,  is  subsequently  absorbed.  On 
the  other  hand,  although  chemically  prepared  casein 
and  cheese  (as  in  the  case  of  Drosera)  excite  much 
acid  secretion,  owing,  I presume,  to  the  absorption  of 
some  included  albuminous  matter,  these  substances 
are  not  digested,  and  are  not  appreciably,  if  at  all, 
reduced  in  bulk. 

Effects  of  the  Vapours  of  Chloroform,  Sulphuric  Ether,  and  Hydro- 
cyanic Acid, — A plant  bearing  one  leaf  was  introduced  into  a 
large  bottle  with  a drachm  (3'549  ml.)  of  chloroform,  the  mouth 
being  imperfectly  closed  with  cotton-wool.  The  vapour  caused 
in  1 m.  the  lobes  to  begin  moving  at  an  imperceptibly  slow  rate ; 
but  in  3 m.  the  spikes  crossed,  and  the  leaf  was  soon  com- 
pletely shut.  The  dose,  however,  was  much  too  large,  for  in 
between  2 and  3 hrs.  the  leaf  appeared  as  if  burnt,  and  soon 
died. 

Two  leaves  were  exposed  for  30  m.  in  a 2-oz.  vessel  to  the 
vapour  of  30  minims  (1*774  ml.)  of  sulphuric  ether.  One  leaf 
closed  after  a time,  as  did  the  other  whilst  being  removed  from 
the  vessel  without  being  touched.  Both  leaves  were  greatly 
injured.  Another  leaf,  exposed  for  20  m.  to  15  minims  of  ether, 
closed  its  lobes  to  a certain  extent,  and  the  sensitive  filaments 
were  now  quite  insensible.  After  24  hrs.  this  leaf  recovered 
its  sensibility,  but  was  still  rather  torpid.  A leaf  exposed 
in  a large  bottle  for  only  3 m.  to  ten  drops  was  rendered 
insensible.  After  52  m.  it  recovered  its  sensibility,  and  when 
one  of  the  filaments  was  touched,  the  lobes  closed.  It  began 


Chap.  XIIL  MANNER  OF  CAPTURING  INSECTS. 


305 


to  reopen  after  20  hrs.  Lastly  another  leaf  was  exposed  for  4 m. 
to  only  four  drops  of  the  ether ; it  was  rendered  insensible,  and 
did  not  close  when  its  filaments  were  repeatedly  touched,  but 
closed  when  the  end  of  the  open  leaf  was  cut  off.  This  shows 
either  that  the  internal  parts  had  not  been  rendered  insensible, 
or  that  an  incision  is  a more  powerful  stimulus  than  repeated 
touches  on  the  filaments.  Whether  the  larger  doses  of  chloro- 
form and  ether,  which  caused  the  leaves  to  close  slowly, 
acted  on  the  sensitive  filaments  or  on  the  leaf  itself,  I do  not 
know. 

Cyanide  of  potassium,  when  left  in  a bottle,  generates  prussic 
or  hydrocyanic  acid.  A leaf  was  exposed  for  1 hr.  35  m.  to  the 
vapour  thus  formed;  and  the  glands  became  within  this  time 
so  colourless  and  shrunken  as  to  be  scarcely  visible,  and  I at 
first  thought  that  they  had  all  dropped  off.  The  leaf  was  not 
rendered  insensible;  for  as  soon  as  one  of  the  filaments  was 
touched  it  closed.  It  had,  however,  suffered,  for  it  did  not 
reopen  until  nearly  two  days  had  passed,  and  was  not  even 
then  in  the  least  sensitive.  After  an  additional  day  it  recovered 
its  powers,  and  closed  on  being  touched  and  subsequently  re- 
opened. Another  leaf  behaved  in  nearly  the  same  manner  after 
a shorter  exposure  to  this  vapour. 

On  the  Manner  in  which  Insects  are  caught, — We  will 
now  consider  the  action  of  the  leaves  when  insects 
happen  to  touch  one  of  the  sensitive  filaments.  This 
often  occurred  in  my  greenhouse,  but  I do  not  know 
whether  insects  are  attracted  in  any  special  way  by 
the  leaves.  They  are  caught  in  large  numbers  by  the 
plant  in  its  native  country.  As  soon  as  a filament  is 
touched,  both  lobes  close  with  astonishing  quickness ; 
and  as  they  stand  at  less  than  a right  angle  to  each 
other,  they  have  a good  chance  of  catching  any  in- 
truder. The  angle  between  the  blade  and  footstalk 
does  not  change  when  the  lobes  close.  The  chief  seat 
of  movement  is  near  the  midrib,  but  is  not  confined 
to  this  part;  for,  as  the  lobes  come  together,  each 
curves  inwards  across  its  whole  breadth ; the  marginal 
spikes  however,  not  becoming  curved.  This  move* 


306 


DION^A  MUSCIPULA. 


Chap.  XIIL 


ment  of  the  whole  lobe  was  well  seen  in  a leaf  to 
which  a large  fly  had  been  given,  and  from  which 
a large  portion  had  been  cut  off  the  end  of  one  lobe ; 
so  that  the  opposite  lobe,  meeting  with  no  re- 
sistance in  this  part,  went  on  curving  inwards  much 
beyond  the  medial  line.  The  whole  of  the  lobe,  from 
which  a portion  had  been  cut,  was  afterwards  removed, 
and  the  opposite  lobe  now  curled  completely  over, 
passing  through  an  angle  of  from  120""  to  130°,  so 
as  to  occupy  a position  almost  at  right  angles  to 
that  which  it  would  have  held  had  the  opposite  lobe 
been  present. 

From  the  curving  inwards  of  the  two  lobes,  as  they 
move  towards  each  other,  the  straight  marginal  spikes 
intercross  by  their  tips  at  first,  and  ultimately  by  their 
bases.  The  leaf  is  then  completely  shut  and  encloses 
a shallow  cavity.  If  it  has  been  made  to  shut  merely 
by  one  of  the  sensitive  filaments  having  been  touched, 
or  if  it  includes  an  object  not  yielding  soluble  nitro- 
genous matter,  the  two  lobes  retain  their  inwardly 
concave  form  until  they  re-expand.  The  re-expansion 
under  these  circumstances — that  is  when  no  organic 
matter  is  enclosed — was  observed  in  ten  cases.  In  all 
of  these,  the  leaves  re-expanded  to  about  two-thirds  of 
the  full  extent  in  24  hrs.  from  the  time  of  closure. 
Even  the  leaf  from  which  a portion  of  one  lobe  had 
been  cut  off  opened  to  a slight  degree  within  this  same 
time.  In  one  case  a leaf  re-expanded  to  about  two- 
thirds  of  the  full  extent  in  7 hrs.,  and  completely  in 
32  hrs. ; but  one  of  its  filaments  had  been  touched 
merely  with  a hail  just  enough  to  cause  the  leaf  to 
close.  Of  these  ten  leaves  only  a few  * re-expanded 
completely  in  less  than  two  days,  and  two  or  three 
required  even  a little  longer  time.  Before,  how- 
ever, they  fully  re-expand,  they  are  ready  to  close 


(Thap.  XIIL  MANNER  OF  CAPTURING  INSECTS.  309 

pensable  for  the  capturing  of  insects.  These  two  move- 
ments, excited  by  two  such  widely  different  means, 
are  thus  both  well  adapted,  like  all  the  other 
functions  of  the  plant,  for  the  purposes  which  they 
subserve. 

There  is  another  wide  difference  in  the  action  of 
leaves  which  enclose  objects,  such  as  bits  of  wood, 
cork,  balls  of  paper,  or  which  have  had  their  filaments 
merely  touched,  and  those  which  enclose  organic 
bodies  yielding  soluble  nitrogenous  matter.  In  the 
former  case  the  leaves,  as  we  have  seen,  open  in  under 
24  hrs.  and  are  then  ready,  even  before  being  fully 
expanded,  to  shut  again.  But  if  they  have  closed 
over  nitrogen-yielding  bodies,  they  remain  closely 
shut  for  many  days;  and  after  re-expanding  are 
torpid,  and  never  act  again,  or  only  after  a consider- 
able interval  of  time.  In  four  instances,  leaves  after 
catching  insects  never  reopened,  but  began  to  wither, 
remaining  closed — in  one  case  for  fifteen  days  over 
a fly ; in  a second,  for  twenty-four  days,  though 
the  fly  was  small ; in  a third  for  twenty-four  days  over 
a woodlouse  ; and  in  a fourth,  for  thirty-five  days  over 
a large  Tipula.  In  two  other  cases  leaves  remained 
closed  for  at  least  nine  days  over  flies,  and  for  how 
many  more  I do  not  know.  It  should,  however,  be 
added  that  in  two  instances  in  which  very  small 
insects  had  been  naturally  caught  the  leaf  opened 
as  quickly  as  if  nothing  had  been  caught ; and  I 
suppose  that  this  was  due  to  such  small  insects  not 
having  been  crushed  or  not  having  excreted  any 
animal  matter,  so  that  the  glands  were  not  excited. 
Small  angular  bits  of  albumen  and  gelatine  were 
placed  at  both  ends  6f  three  leaves,  two  of  which 
remained  closed  for  thirteen  and  the  other  for  twelve 
days.  Two  other  leaves  remained  closed  over  bits  of 


310 


DIOlS^A  MUSCIPULA. 


Chap.  XIII. 


meat  for  eleven  days,  a third  leaf  for  eight  days,  and 
a fourth  (but  this  had  been  cracked  and  injured)  for 
only  six  days.  Bits  of  cheese,  or  casein,  were  placed 
at  one  end  and  albumen  at  the  other  end  of  three 
leaves;  and  the  ends  with  the  former  opened  after 
six,  eight,  and  nine  days,  whilst  the  opposite  ends 
opened  a little  later.  None  of  the  above  bits  of  meat, 
albumen,  &c.,  exceeded  a cube  of  -V  of  ii^oh 
(2’54  mm.)  in  size,  and  were  sometimes  smaller ; yet 
these  small  portions  sufficed  to  keep  the  leaves  closed 
for  many  days.  Dr.  Canby  informs  me  that  leaves 
remain  shut  for  a longer  time  over  insects  than  over 
meat ; and  from  what  I have  seen,  I can  well  believe 
that  this  is  the  case,  especially  if  the  insects  are 
large. 

In  all  the  above  cases,  and  in  many  others  in  which 
leaves  remained  closed  for  a long  but  unknown 
period  over  insects  naturally  caught,  they  were  more 
or  less  torpid  when  they  reopened.  Generally  they 
were  so  torpid  during  many  succeeding  days  that  no 
excitement  of  the  filaments  caused  the  least  move- 
ment. In  one  instance,  however,  on  the  day  after  a 
leaf  opened  which  had  clasped  a fly,  it  closed  with  ex- 
treme slowness  when  one  of  its  filaments  was  touched ; 
and  although  no  object  was  left  enclosed,  it  was  so 
torpid  that  it*  did  not  re-open  for  the  second  time 
until  44  hrs.  had  elapsed.  In  a second  case,  a leaf 
which  had  expanded  after  remaining  closed  for  at 
least  nine  days  over  a fly,  when  greatly  irritated, 
moved  one  alone  of  its  two  lobes,  and  retained  this 
unusual  position  for  the  next  two  days.  A third  case 
offers  the  strongest  exception  which  I have  observed  ; 
a leaf,  after  remaining  clasped  for  an  unknown  time 
over  a fly,  opened,  and  when  one  of  its  filaments  was 
touched,  closed,  though  rather  slowly.  Dr.  Canbyt 


Chap.  Xm.  MANNER  OF  CAPTURING  INSECTS.  311 

who  observed  in  the  United  States  a large  number  of 
plants  which,  although  not  in  their  native  site,  were 
probably  more  vigorous  than  my  plants,  informs 
me  that  he  has  several  times  known  vigorous  leaves 
to  devour  their  prey  several  times ; but  ordinarily 
twice,  or,  quite  often,  once  was  enough  to  render  them 
unserviceable.”  Mrs.  Treat,  who  cultivated  many 
plants  in  New  Jersey,  also  informs  me  that  several 
leaves  caught  successively  three  insects  each,  but  most 
of  them  were  not  able  to  digest  the  third  fly,  but  died 
in  the  attempt.  Five  leaves,  however,  digested  each 
three  flies,  and  closed  over  the  fourth,  but  died  soon 
after  the  fourth  capture.  Many  leaves  did  not  digest 
even  one  large  insect.”  It  thus  appears  that  the 
power  of  digestion  is  somewhat  limited,  and  it  is 
certain  that  leaves  always  remain  clasped  for  many 
days  over  an  insect,  and  do  not  recover  their  power  of 
closing  again  for  many  subsequent  days.  In  this 
respect  Dionsea  differs  from  Drosera,  which  catches 
and  digests  many  insects  after  shorter  intervals  of 
time. 

We  are  now  prepared  to  understand  the  use  of  the 
marginal  spikes,  which  form  so  conspicuous  a feature 
. in  the  appearance  of  the  plant  (fig.  12,  p.  287),  and 
which  at  first  seemed  to  me  in  my  ignorance  useless 
appendages.  From  the  inward  curvature  of  the  lobes 
as  they  approach  each  other,  the  tips  of  the  marginal 
spikes  first  intercross,  and  ultimately  their  bases. 
Until  the  edges  of  the  lobes  come  into  contact,  elon- 
gated spaces  between  the  spikes,  varying  from  the  -j-U- 
to  the  -jV  of  an  inch  (1*693  to  2*54  mm.)  in  breadth, 
according  to  the  size  of  the  leaf,  are  left  open.  Thus 
an  insect,  if  its  body  is  not  thicker  than  these  mea- 
surements, can  easily  escape  between  the  crossed 
spikes,  when  disturbed  by  the  closing  lobes  and  in 


312 


DION^A  MUSCIPULa. 


Chap.  XIII. 


creasing  darkness ; and  one  of  my  sons  actually  saw  a 
small  insect  thus  escaping.  A moderately  large  in- 
sect, on  the  other  hand,  if  it  tries  to  escape  between 
the  bars  will  surely  be  pushed  back  again  into  its 
horrid  prison  with  closing  walls,  for  the  spikes  con- 
tinue to  cross  more  and  more  until  the  edges  of  the 
lobes  come  into  contact.  A very  strong  insect,  how- 
eyer,  would  be  able  to  free  itself,  and  Mrs.  Treat  saw 
this  effected  by  a rose-chafer  {Macrodactylus  subspi- 
nosus)  in  the  United  States.  Now  it  would  manifestly 
be  a great  disadvantage  to  the  plant  to  waste  many 
days  in  remaining  clasped  over  a minute  insect,  and 
several  additional  days  or  weeks  in  afterwards  re- 
covering its  sensibility ; inasmuch  as  a minute  insect 
would  afford  but  little  nutriment.  It  would  be 
far  better  for  dhe  plant  to  wait  for  a time  until  a 
moderately  large  insect  was  captured,  and  to  allow  all 
the  little  ones  to  escape ; and  this  advantage  is 
secured  by  the  slowly  intercrossing  marginal  spikes, 
which  act  like  the  large  meshes  of  a fishing-net, 
allowing  the  small  and  useless  fry  to  escape. 

As  I was  anxious  to  know  whether  this  view  was 
correct— and  as  it  seems  a good  illustration  of  how 
cautious  we  ought  to  be  in  assuming,  as  I had  done 
with  respect  to  the  marginal  spikes,  that  any  fully 
developed  structure  is  useless — I applied  to  Dr.  Canby. 
He  visited  the  native  site  of  the  plant,  early  in  the 
season,  before  the  leaves  had  grown  to  their  full  size, 
and  sent  me  fourteen  leaves,  containing  naturally 
captured  insects.  Four  of  these  had  caught  rather 
small  insects,  viz.  three  of  them  ants,  and  the  fourth 
a rather  small  fly,  but  the  other  ten  had  all  caught 
large  insects,  namely,  five  elaters,  two  chrysomelas, 
a curculio,  a thick  and  broad  spider,  and  a scolo- 
pendra.  Out  of  these  ten  insects,  no  less  than  eight 


Ohap.  XIII.  TEANSMISSION  OF  MOTOR  IMPULSE.  313 


were  beetles,^  and  out  of  the  whole  fourteen  there 
was  only  one,  viz.  a dipterous  insect,  which  could 
readily  take  flight.  Drosera,  on  the  other  hand, 
lives  chiefly  on  insects  which  are  good  flyers,  especially 
Diptera,  caught  by  the  aid  of  its  viscid  secretion.  But 
what  most  concerns  us  is  the  size  of  the  ten  larger 
insects.  Their  average  length  from  head  to  tail  was 
•256  of  an  inch,  the  lobes  of  the  leaves  being  on  an 
average  *53  of  an  inch  in  length,  so  that  the  insects 
were  very  nearly  half  as  long  as  the  leaves  within 
which  they  were  enclosed.  Only  a few  of  these  leaves, 
therefore,  had  wasted  their  powers  by  capturing  small 
prey,  though  it  is  probable  that  many  small  insects 
had  crawled  over  them  and  been  caught,  but  had 
then  escaped  through  the  bars. 

The  Transmission  of  the  Motor  Impulse,  and  Means 
of  Movement. — It  is  sufficient  to  touch  any  one  of  the 
six  filaments  to  cause  both  lobes  to  close,  these  becom- 
ing at  the  same  time  incurved  throughout  their  whole 
breadth.  The  stimulus  must  therefore  radiate  in  all 
directions  from  any  one  filament.  It  must  also  be 
transmitted  with  much  rapidity  across  the  leaf,  for  in 
all  ordinary  cases  both  lobes  close  simultaneously, 
as  far  as  the  eye  can  judge.  Most  physiologists  be- 
lieve that  in  irritable  plants  the  excitement  is  trans- 
mitted along,  or  in  close  connection  with,  the  fibro- 
vascular  bundles.  In  Dionsea,  the  course  of  these 
vessels  (composed  of  spiral  and  ordinary  vascular 


* Dr.  Canby  remarks  Gar- 
dener’s Monthly/  August  1868), 
“as  a general  thing  beetles  and 
insects  of  that  kind,  though  al- 
ways killed,  seem  to  be  too  hard- 
shelled  to  serve  as  food,  and  after 
a short  time  are  rejected.”  I am 
surprised  at  this  statement,  at 
least  with  respect  to  such  beetles 


as  elaters,  for  the  five  which  I 
examined  were  in  an  extremely 
fragile  and  empty  condition,  as  if 
all  their  internal  parts  had  been 
partially  digested.  Mrs.  Treat 
informs  me  that  the  plants  which 
she  cultivated  in  New  Jersey 
chiefly  caught  Diptera. 


314 


DION^A  MUSCIPULA. 


Chap.  XIIL 


tissue)  seems  at  first  sight  to  favour  this  belief;  for 
they  run  up  the  midrib  in  a great  bundle,  sending 
off  small  bundles  almost  at  right  angles  on  each  side. 
These  bifurcate  occasionally  as  they  extend  towards 
the  margin,  and  close  to  the  margin  small  branches 
from  adjoining  vessels  unite  and  enter  the  marginal 
spikes.  At  some  of  these  points  of  union  the  vessels 
form  curious  loops,  like  those  described  under  Drosera. 
A continuous  zigzag  line  of  vessels  thus  runs  round 
the  whole  circumference  of  the  leaf,  and  in  the  midrib 
all  the  vessels  are  in  close  contact ; so  that  all  parts  of 
the  leaf  seem  to  be  brought  into  some  degree  of  com- 
munication. Nevertheless,  the  presence  of  vessels  is 
not  necessary  for  the  transmission  of  the  motor 
impulse,  for  it  is  transmitted  from  the  tips  of  the 
sensitive  filaments  (these  being  about  the  of  an 
inch  in  length),  into  which  no  vessels  enter ; and 
these  could  not  have  been  overlooked,  as  I made  thin 
vertical  sections  of  the  leaf  at  the  bases  of  the  fila- 
ments. 

On  several  occasions,  slits  about  the  -j-V  of  an  inch 
in  length  were  made  with  a lancet,  close  to  the  bases 
of  the  filaments,  parallel  to  the  midrib,  and,  there- 
fore, directly  across  the  course  of  the  vessels.  These 
were  made  sometimes  on  the  inner  and  sometimes 
on  the  outer  sides  of  the  filaments ; and  after  several 
days,  when  the  leaves  had  reopened,  these  filaments 
were  touched  roughly  (for  they  were  always  rendered 
in  some  degree  torpid  by  the  operation),  and  the 
lobes  then  closed  in  the  ordinary  manner,  though 
slowly,  and  sometimes  not  until  after  a considerable 
interval  of  time.  These  cases  show  that  the  motor 
impulse  is  not  transmitted  along  the  vessels,  and  they 
further  show  that  there  is  no  necessity  for  a direct 
line  of  communication  from  the  filament  which  is 


JiiAP.  XIII.  TRANSMISSION  OF  MOTOR  IMPULSE.  315 

touched  towards  the  midrib  and  opposite  lobe,  or 
towards  the  outer  parts  of  the  same  lobe. 

Two  slits  near  each  other,  both  parallel  to  the  mid-  \ 
rib,  were  next  made  in  the  same  manner  as  before,  one  f 
on  each  side  of  the  base  of  a filament,  on  five  distinct 
leaves,  so  that  a little  slip  bearing  a filament  was  con- 
nected with  the  rest  of  the  leaf  only  at  its  two  ends. 
These  slips  were  nearly  of  the  same  size ; one  was  care- 
fully measured ; it  was  *12  of  an  inch  (3’048  mm.)  in 
length,  and  *08  of  an  inch  (2*032  mm.)  in  breadth; 
and  in  the  middle  stood  the  filament.  Only  one  of 
these  slips  withered  and  perished.  After  the  leaf  had 
recovered  from  the  operation,  though  the  slits  were 
still  open,  the  filaments  thus  circumstanced  were 
roughly  touched,  and  both  lobes,  or  one  alone,  slowly 
closed.  In  two  instances  touching  the  filament  pro- 
duced no  effect ; but  when  the  point  of  a needle  was 
driven  into  the  slip  at  the  base  of  the  filament,  the 
lobes  slowly  closed.  Now  in  these  cases  the  impulse 
must  have  proceeded  along  the  slip  in  a line  parallel 
to  the  midrib,  and  then  have  radiated  forth,  either 
from  both  ends  or  from  one  end  alone  of  the  slip,  over 
the  whole  surface  of  the  two  lobes. 

Again,  two  parallel  slits,  like  the  former  ones,  were 
made,  one  on  each  side  of  the  base  of  a filament,  at 
right  angles  to  the  midrib.  After  the  leaves  (two  in 
number)  had  recovered,  the  filaments  were  roughly 
touched,  and  the  lobes  slowly  closed;  and  here  the 
impulse  must  have  travelled  for  a short  distance  in  a 
line  at  right  angles  to  the  midrib,  and  then  have 
radiated  forth  on  all  sides  over  both  lobes.  These 
several  cases  prove  that  the  motor  impulse  travels  in 
all  directions  through  the  cellular  tissue,  independently 
of  the  course  of  the  vessels. 

With  Drosera  we  have  seen  that  the  motor  impulse 


316 


DION^A  MUSCIPULA. 


Chap.  XIII. 


is  transmitted  in  like  manner  in  all  directions  through 
the  cellular  tissue ; but  that  its  rate  is  largely  governed 
by  the  length  of  the  cells  and  the  direction  of  their 
longer  axes,  thin  sections  of  a leaf  of  Dionaea  were 
made  by  my  son,  and  the  cells,  both  those  of  the 
central  and  of  the  more  superficial  layers,  were  foimd 
much  elongated,  with  their  longer  axes  directed  to- 
wards the  midrib ; and  it  is  in  this  direction  that  the 
motor  impulse  must  be  sent  with  great  rapidity  from 
one  lobe  to  the  other,  as  both  close  simultaneously. 
The  central  parenchymatous  cells  are  larger,  more 
loosely  attached  together,  and  have  more  delicate  walls 
than  the  more  superficial  cells.  A thick  mass  of  ceh 
lular  tissue  forms  the  upper  surface  of  the  midrib 
over  the  great  central  bundle  of  vessels. 

When  the  filaments  were  roughly  touched,  at  the 
bases  of  which  slits  had  been  made,  either  on  both 
sides  or  on  one  side,  parallel  to  the  midrib  or  at  right 
angles  to  it,  the  two  lobes,  or  only  one,  moved.  In 
one  of  these  cases,  the  lobe  on  the  side  which  bore  the 
filament  that  was  touched  moved,  but  in  three  other 
cases  the  opposite  lobe  alone  moved  ; so  that  an  injury 
which  was  sufficient  to  prevent  a lobe  moving  did  not 
prevent  the  transmission  from  it  of  a stimulus  which 
excited  the  opposite  lobe  to  move.  We  thus  also 
learn  that,  although  normally  both  lobes  move  to- 
gether, each  has  the  power  of  independent  movement. 
A case,  indeed,  has  already  been  given  of  a torpid 
leaf  that  had  lately  re-opened  after  catching  an 
insect,  of  which  one  lobe  alone  moved  when  irritated. 
Moreover,  one  end  of  the  same  lobe  can  close  and  re- 
expand, independently  of  the  other  end,  as  was  seen 
in  some  of  the  foregoing  experiments. 

When  the  lobes,  which  are  rather  thick,  close,  no  trace 
of  wrinkling  can  be  seen  on  any  part  of  their  upper 


Chat.  XIII.  TRANSMISSION  OF  MOTOR  IMPULSE.  317 

surfaces.  It  appears  therefore  that  the  cells  must  con- 
tract. The  chief  seat  of  the  movement  is  evidently 
in  the  thick  mass  of  cells  which  overlies  the  central 
bundle  of  vessels  in  the  midrib.  To  ascertain  whether 
this  part  contracts,  a leaf  was  fastened  on  the  stage  of 
the  microscope  in  such  a manner  that  the  two  lobes 
could  not  become  quite  shut,  and  having  made  two 
minute  black  dots  on  the  midrib,  in  a transverse  line 
and  a little  towards  one  side,  they  were  found  by  the 
micrometer  to  be  -fil-o  apart.  One  of  the 

filaments  was  then  touched  and  the  lobes  closed ; but 
as  they  were  prevented  from  meeting,  I could  still  see 
the  two  dots,  which  now  were  of  an  inch  apart, 
so  that  a small  portion  of  the  upper  surface  of  the 
midrib  had  contracted  in  a transverse  line  toito  of  an 
inch  (’0508  mm.). 

We  know  that  the  lobes,  whilst  closing,  become 
slightly  incurved  throughout  their  whole  breadth. 
This  movement  appears  to  be  due  to  the  contraction 
of  the  superficial  layers  of  cells  over  the  whole  upper 
surface.  In  order  to  observe  their  contraction,  a nar- 
row strip  was  cut  out  of  one  lobe  at  right  angles  to 
the  midrib,  so  that  the  surface  of  the  opposite  lobe 
could  be  seen  in  this  part  when  the  leaf  was  shut. 
After  the  leaf  had  recovered  from  the  operation  and 
had  re-expanded,  three  minute  black  dots  were  made 
on  the  surface  opposite  to  the  slit  or  window,  in  a line 
at  right  angles  to  the  midrib.  The  distance  between 
the  dots  was  found  to  be  tH-o  inch,  so  that  the 

two  extreme  dots  were  ttw  apart.  One  of 

the  filaments  was  now  touched  and  the  leaf  closed. 
On  again  measuring  the  distances  between  the  dots, 
the  two  next  to  the  midrib  were  nearer  together  by 
•j-wo'  inch,  and  the  two  further  dots  by  of 

an  inch,  than  they  were  before  ; so  that  the  two  extreme 


318 


DION^A  MUSCIPULA. 


Chap.  XIII. 


dots  now  stood  about  -j-oVo  (*127  mm.) 

nearer  together  than  before.  If  we  suppose  the  whole 
upper  surface  of  the  lobe,  which  was  of  an  inch 
in  breadth,  to  have  contracted  in  the  same  proportion, 
the  total  contraction  will  have  amounted  to  about 
or  (*635  mm.) ; but  whether  this 

is  sufficient  to  account  for  the  slight  inward  curvature 
of  the  whole  lobe,  I am  unable  to  say. 

Finally,  with  respect  to  the  movement  of  the  leaves, 
the  wonderful  discovery  made  by  Dr.  Burdon  Sander- 
son* is  now  universally  known ; namely  that  there 
exists  a normal  electrical  current  in  the  blade  and 
footstalk ; and  that  when  the  leaves  are  irritated,  the 
current  is  disturbed  in  the  same  manner  as  takes  place 
during  the  contraction  of  the  muscle  of  an  animal. 

The  Re-expansion  of  the  Leaves. — This  is  effected  at  an 
insensibly  slow  rate,  whether  or  not  any  object  is 
enclosed.!  One  lobe  can  re-expand  by  itself,  as  oc- 
curred with  the  torpid  leaf  of  which  one  lobe  alone  had 
closed.  We  have  also  seen  in  the  experiments  with 
cheese  and  albumen  that  the  two  ends  of  the  same  lobe 
can  re-expand  to  a certain  extent  independently  of 
each  other.  But  in  all  ordinary  cases  both  lobes  open 
at  the  same  time.  The  re-expansion  is  not  determined 
by  the  sensitive  filaments ; all  three  filaments  on  one 
lobe  were  cut  off  close  to  their  bases ; and  the  three 


‘Proc.  Koyal  Soc.*  vol.  xxi. 
p.  495 ; and  lecture  at  the  Royal 
Institution,  June  5, 1874,  given  in 
‘Nature,’  1874,  pp.  105  and  127. 

t Nuttall,  in  his  ‘ Gen.  Ame- 
rican Plants,’  p.  277  (note),  says 
that,  whilst  collecting  this  plant 
in  its  native  home,  “ I had  occa- 
sion to  observe  that  a detached 
leaf  would  make  repeated  efforts 
towards  disclosing  itself  to  the 


influence  of  the  sun ; these  at- 
tempts consisted  in  an  undula- 
tory  motion  of  the  marginal  cilias, 
accompanied  by  a partial  open- 
ing and  succeeding  collapse  of 
the  lamina,  which  at  length  ter- 
minated in  a complete  expansion 
and  in  the  destruction  of  sensi- 
bility.” I am  indebted  to  Prof. 
Oliver  for  this  reference ; but  I dtf 
not  understand  what  took  place. 


Chap.  XIIL 


RE-EXPANSION. 


319 


leaves  thus  treated  re-expanded, — one  to  a partial  ex- 
tent in  24  hrs.j — a second  to  the  same  extent  in  48 
hrs., — and  the  third,  which  had  been  previously  in- 
jured, not  until  the  sixth  day.  These  leaves  after 
their  re-expansion  closed  quickly  when  the  filaments 
on  the  other  lobe  were  irritated.  These  were  then  cut 
olf  one  of  the  leaves,  so  that  none  were  left.  This 
mutilated  leaf,  notwithstanding  the  loss  of  all  its  fila- 
ments, re-expanded  in  two  days  in  the  usual  manner. 
When  the  filaments  have  been  excited  by  immersion 
in  a solution  of  sugar,  the  lobes  do  not  expand  so  soon 
as  when  the  filaments  have  been  merely  touched ; and 
this,  I presume,  is  due  to  their  having  been  strongly 
affected  through  exosmose,  so  that  they  continue  for 
some  time  to  transmit  a motor  impulse  to  the  upper 
surface  of  the  leaf. 

The  following  facts  make  me  believe  that  the 
several  layers  of  cells  forming  the  lower  surface  of  the 
leaf  are  always  in  a state  of  tension ; and  that  it  is 
owing  to  this  mechanical  state,  aided  probably  by 
fresh  fluid  being  attracted  into  the  cells,  that  the  lobes 
begin  to  separate  or  expand  as  soon  as  the  contraction 
of  the  upper  surface  diminishes.  A leaf  was  cut  off 
and  suddenly  plunged  perpendicularly  into  boiling 
water : I expected  that  the  lobes  would  have  closed, 
but  instead  of  doing  so,  they  diverged  a little.  I then 
took  another  fine  leaf,  with  the  lobes  standing  at  an 
angle  of  nearly  80°  to  each  other ; and  on  immersing 
it  as  before,  the  angle  suddenly  increased  to  90°.  A 
third  leaf  was  torpid  from  having  recently  re-expanded 
after  having  caught  a fly,  so  that  repeated  touches  of 
the  filaments  caused  not  the  least  movement;  never- 
theless, when  similarly  immersed,  the  lobes  separated  a 
little.  As  these  leaves  were  inserted  perpendicularly 
into  the  boiling  water,  both  surfaces  and  the  filaments 


320 


DION^A  MUSCIPULA. 


Chap.  XUI. 


must  have  been  equally  affected ; and  1 can  under- 
stand the  divergence  of  the  lobes  only  by  supposing 
that  the  cells  on  the  lower  side,  owing  to  their  state  of 
tension,  acted  mechanically  and  thus  suddenly  drew 
the  lobes  a little  apart,  as  soon  as  the  cells  on  the 
upper  surface  were  killed  and  lost  their  contractile 
power.  We  have  seen  that  boiling  water  in  like 
manner  causes  the  tentacles  of  Drosera  to  curve  back- 
wards ; and  this  is  an  analogous  movement  to  the 
divergence  of  the  lobes  of  Dionsea. 

In  some  concluding  remarks  in  the  fifteenth  chapter 
on  the  DroseracesD,  the  different  kinds  of  irritability 
possessed  by  the  several  genera,  and  the  different 
manner  in  which  they  capture  insects,  will  be  com- 
pared. 


CHAr.  XIV. 


ALDEOVANDA  VESICULOSA. 


321 


CHAPTEE  XIV. 

Aldrovanda  vesiculosa. 

Captures  crustaceans  — Structure  of  the  leaves  in  comparison  with 
those  of  Dionaea — Absorption  by  the  glands,  by  the  quadrifid  pro- 
cesses, and  points  on  the  infolded  margins  — Aldrovanda  vesiculosa, 
var.  australis  — Captures  prey  — Absorption  of  animal  matter  — 
Aldrovanda  vesiculosa,  var.  verticillata  — Concluding  remarks. 

This  plant  may  be  called  a miniature  aquatic  Dionsea. 
Stein  discovered  in  1873  that  the  bilobed  leaves, 
which  are  generally  found  closed  in  Europe,  open 
under  a sufficiently  high  temperature,  and,  when 
touched,  suddenly  close.*  They  re-expand  in  from 
24  to  36  hrs.,  but  only,  as  it  appears,  when  inor- 
ganic objects  are  enclosed.  The  leaves  sometimes 
contain  bubbles  of  air,  and  were  formerly  supposed  to 
be  bladders ; hence  the  specific  name  of  vesiculosa. 
Stein  observed  that  water-insects  were  sometimes 
caught,  and  Prof.  Cohn  has  recently  found  within  the 
leaves  of  naturally  growing  plants  many  kinds  of 
crustaceans  and  larvae.f  Plants  which  had  been  kept 
in  filtered  water  were  placed  by  him  in  a vessel  con- 


* Since  his  original  publication, 
Stein  has  found  out  that  the  irri- 
tability of  the  leaves  was  observed 
by  De  Sassus,  as  recorded  in 
‘ Bull.  Bot.  Soc.  de  France,*  in 
1861.  Delpino  states  in  a paper 
published  in  1871  (‘Nuovo  Gior- 
nale  Bot.  Ital.*  vol.  iii.  p.  174) 
that  “una  quantity  di  chioccio- 
line  e di  altri  animalcoli  acqua- 
tici**  are  caught  and  suffocated 

by  the  leaves.  I presume  that 


chioccioline  are  fresh-water  mol- 
luscs. It  would  be  interesting  to 
know  whether  their  shells  are  at 
all  corroded  by  the  acid  of  the 
digestive  secretion. 

t I am  greatly  indebted  to  this 
distinguished  naturalist  for  having 
sent  me  a copy  of  his  memoir  on 
Aldrovanda,  before  its  publica- 
tion in  his  ‘ Beitrage  zur  Biologie 
der  Pflanzen,*  drittes  Heft,  1875, 
p.  71. 


322 


ALDROVANDA  VESICULOSA. 


Chap.  XIV. 


taining  numerous  crustaceans  of  the  genus  Cypris,  and 
next  morning  many  were  found  imprisoned  and  alive, 
still  swimming  about  within  the  closed  leaves,  but 
doomed  to  certain  death. 

Directly  after  reading  Prof.  Cohn’s  memoir,  I re- 
ceived through  the  kindness  of  Dr.  Hooker  living 
plants  from  Germany.  As  I can  add  nothing  to  Prof. 
Cohn’s  excellent  description,  I will  give  only  two 
illustrations,  one  of  a whorl  of  leaves  copied  from  his 
work,  and  the  other  of  a leaf  pressed  flat  open,  drawn 
by  my  son  Francis.  I will,  however,  append  a few 
remarks  on  the  differences  between  this  plant  and 
Dionsea. 

Aldrovanda  is  destitute  of  roots  and  floats  freely  in 
the  water.  The  leaves  are  arranged  in  whorls  round 
the  stem.  Their  broad  petioles  terminate  in  from  four 
to  six  rigid  projections,*  each  tipped  with  a stiff, 
short  bristle.  The  bilobed  leaf,  with  the  midrib  like- 
wise tipped  with  a bristle,  stands  in  the  midst  of 
these  projections,  and  is  evidently  defended  by  them. 
The  lobes  are  formed  of  very  delicate  tissue,  so  as  to 
be  translucent ; they  open,  according  to  Cohn,  about 
as  much  as  the  two  valves  of  a living  mussel-shell, 
therefore  even  less  than  the  lobes  of  Dionaea ; and 
this  must  make  the  capture  of  aquatic  animals  more 
easy.  The  outside  of  the  leaves  and  the  petioles  are 
covered  with  minute  two-armed  papillae,  evidently 
answering  to  the  eight-rayed  papillae  of  Dionaea. 

Each  lobe  rather  exceeds  a semi-circle  in  convexity, 
and  consists  of  two  very  different  concentric  portions  ; 
the  inner  and  lesser  portion,  or  that  next  to  the  midrib, 


* There  has  been  much  discus-  1861,  p.  146)  believes  that  they 
sion  by  botanists  on  the  homologi-  correspond  with  the  fimbriated 
cal  nature  of  these  projections  scale-like  bodies  found  at  the 
Dr.  Nitschke  (•  Bot.  Zeitung,  bases  of  the  petioles  of  Drosera. 


Chap.  XIV. 


ALDROVANDA  VESICULOSA. 


323 


is  slightly  concave,  and  is  formed,  according  to  Cohn, 
of  three  layers  of  cells.  Its  upper  surface  is  studded 
with  colourless  glands  like,  but  more  simple  than, 
those  of  Dionsea ; they  are  supported  . on  distinct 
footstalks,  consisting  of  two  rows  of  cells.  The  outer 


Fig.  13. 

{Aldrovanda  vesiculosa.) 

Upper  figure,  whorl  of  leaves  (from  Prof.  Cohn). 

Lower  figure,  leaf  pressed  flat  open  and  greatly  enlarged. 

and  broader  portion  of  the  lobe  is  flat  and  very 
thin,  being  formed  of  only  two  layers  of  cells.  Its 
upper  surface  does  not  bear  any  glands,  but,  in  their 
place,  small  quadrifid  processes,  each  consisting  of 
four  tapering  projections,  which  rise  from  a common 


324  ALDROVANDA  VESICULOSA.  Chap.  XIV. 

prominence.  These  processes  are  formed  of  very 
delicate  membrane  lined  with  a layer  of  protoplasm ; 
and  they  sometimes  contain  aggregated  globules  of 
hyaline  matter.  Two  of  the  slightly  diverging  arms 
are  directed  towards  the  circumference,  and  two 
towards  the  midrib,  forming  together  a sort  of  Greek 
cross.  Occasionally  two  of  the  arms  are  replaced  by 
one,  and  then  the  projection  is  trifid.  We  shall  see  in 
a future  chapter  that  these  projections  curiously  re- 
semble those  found  within  the  bladders  of  Utricularia, 
more  especially  of  Utricularia  montana,  although  this 
genus  is  not  related  to  Aldrovanda. 

A narrow  rim  of  the  broad  flat  exterior  part  of  each 
lobe  is  turned  inwards,  so  that,  when  the  lobes  are 
closed,  the  exterior  surfaces  of  the  in-folded  portions 
come  into  contact.  The  edge  itself  bears  a row  of 
conical,  flattened,  transparent  points  with  broad  bases, 
like  the  prickles  on  the  stem  of  a bramble  or  Eubus. 
As  the  rim  is  infolded,  these  points  are  directed 
towards  the  midrib,  and  they  appear  at  first  as  if  they 
were  adapted  to  prevent  the  escape  of  prey ; but  this 
can  hardly  be  their  chief  function,  for  they  are  com- 
posed of  very  delicate  and  highly  flexible  membrane, 
which  can  be  easily  bent  or  quite  doubled  back  with- 
out being  cracked.  Nevertheless,  the  infolded  rims, 
together  with  the  points,  must  somewhat  interfere 
with  the  retrograde  movement  of  any  small  creature, 
as  soon  as  the  lobes  begin  to  close.  The  circum- 
ferential part  of  the  leaf  of  Aldrovanda  thus  differs 
greatly  from  that  of  Dionaea;  nor  can  the  points  on 
the  rim  be  considered  as  homologous  with  the  spikes 
round  the  leaves  of  Dionaea,  as  these  latter  are  pro- 
longations of  the  blade,  and  not  mere  epidermic 
productions.  They  appear  also  to  serve  for  a widely 
different  purpose. 


Chap.  XIV. 


ALDROVANDA  VESICULOSA. 


325 


On  the  concave  gland-bearing  portion  of  the  lobes, 
and  especially  on  the  midrib,  there  are  numerous, 
long,  finely  pointed  hairs,  which,  as  Prof.  Cohn  re- 
marks, there  can  be  little  doubt  are  sensitive  to  a 
touch,  and,  when  touched,  cause  the  leaf  to  close. 
They  are  formed  of  two  rows  of  cells,  or,  according  to 
Cohn,  sometimes  of  four,  and  do  not  include  any  vas- 
cular tissue.  They  differ  also  from  the  six  sensitive 
filaments  of  DionaGa  in  being  colourless,  and  in  having 
a medial  as  well  as  a basal  articulation.  No  doubt  it 
is  owing  to  these  two  articulations  that,  notwithstand- 
ing their  length,  they  escape  being  broken  when  the 
lobes  close. 

The  plants  which  I received  during  the  early  part 
of  October  from  Kew  never  opened  their  leaves, 
though  subjected  to  a high  temperature.  After  ex- 
amining the  structure  of  some  of  them,  I experimented 
on  only  two,  as  I hoped  that  the  plants  would  grow ; 
and  I now  regret  that  I did  not  sacrifice  a greater 
number. 

A leaf  was  cut  open  along  the  midrib,  and  the 
glands  examined  under  a high  power.  It  was  then 
placed  in  a few  drops  of  an  infusion  of  raw  meat. 
After  3 hrs.  20  m.  there  was  no  change,  but  when 
next  examined  after  23  hrs.  20  m.,  the  outer  cells  of 
the  glands  contained,  instead  of  limpid  fluid,  spherical 
masses  of  a granular  substance,  showing  that  matter 
had  been  absorbed  from  the  infusion.  That  these 
glands  secrete  a fluid  which  dissolves  or  digests  animal 
matter  out  of  the  bodies  of  the  creatures  which  the 
leaves  capture,  is  also  highly  probable  from  the 
analogy  of  Dionsea.  If  we  may  trust  to  the  same 
analogy,  the  concave  and  inner  portions  of  the  two 
lobes  probably  close  together  by  a slow  movement,  as 
soon  as  the  glands  have  absorbed  a slight  amount  of 


326 


ALDROVANDA  VESICULOSA. 


Chap.  XIV 


already  soluble  animal  matter.  The  included  water 
would  thus  be  pressed  out,  and  the  secretion  conse- 
quently not  be  too  much  diluted  to  act.  With  respect 
to  the  quadrifid  processes  on  the  outer  parts  of  the 
lobes,  I was  not  able  to  decide  whether  they  had  been 
acted  on  by  the  infusion;  for  the  lining  of  proto- 
plasm was  somewhat  shrunk  before  they  were  im- 
mersed. Many  of  the  points  on  the  infolded  rims 
also  had  their  lining  of  protoplasm  similarly  shrunk, 
and  contained  spherical  granules  of  hyaline  matter. 

A solution  of  urea  was  next  employed.  This  sub- 
stance was  chosen  partly  because  it  is  absorbed  by  the 
quadrifid  processes  and  more  especially  by  the  glands 
of  Utricularia — a plant  which,  as  we  shall  hereafter  see, 
feeds  on  decayed  animal  matter.  As  urea  is  one  of  the 
last  products  of  the  chemical  changes  going  on  in  the 
living  body,  it  seems  fitted  to  represent  the  early  stages 
of  the  decay  of  the  dead  body.  I was  also  led  to  try 
urea  from  a curious  little  fact  mentioned  by  Prof. 
Cohn,  namely  that  when  rather  large  crustaceans  are 
caught  between  the  closing  lobes,  they  are  pressed  so 
hard  whilst  making  their  escape  that  they  often  void 
their  sausage-shaped  masses  of  excrement,  which  were 
found  within  most  of  the  leaves.  These  masses,  no 
doubt,  contain  urea.  They  would  be  left  either  on 
the  broad  outer  surfaces  of  the  lobes  where  the  quad- 
rifids  are  situated,  or  within  the  closed  concavity.  In 
the  latter  case,  water  charged  with  excrementitious 
and  decaying  matter  would  be  slowly  forced  outwards, 
and  would  bathe  the  quadrifids,  if  I am  right  in 
believing  that  the  concave  lobes  contract  after  a time 
like  those  of  Dionaea.  Foul  w^ater  would  also  be  apt 
to  ooze  out  at  all  times,  especially  when  bubbles  of  air 
were  generated  within  the  concavity. 

A leaf  was  cut  open  and  examined,  and  the  outer 


Chap.  XIV. 


ALDROVANDA  VESICULOSA. 


327 


cells  of  the  glands  were  found  to  contain  only  limpid 
fluid.  Some  of  the  quadrifids  included  a few  spherical 
granules,  but  several  were  transparent  and  empty,  and 
their  positions  were  marked.  This  leaf  was  now  im- 
mersed in  a little  solution  of  one  part  of  urea  to  146 
of  water,  or  three  grains  to  the  ounce.  After  3 hrs. 
40  m.  there  was  no  change  either  in  the  glands  or 
quadrifids ; nor  was  there  any  certain  change  in  the 
glands  after  24  hrs. ; so  that,  as  far  as  one  trial  goes, 
urea  does  not  act  on  them  in  the  same  manner  as 
an  infusion  of  raw  meat.  It  was  different  with  the 
quadrifids ; for  the  lining  of  protoplasm,  instead  of 
presenting  a uniform  texture,  was  now  slightly  shrunk, 
and  exhibited  in  many  places  minute,  thickened,  irre- 
gular, yellowish  specks  and  ridges,  exactly  like  those 
which  appear  within  the  quadrifids  of  Utricularia 
when  treated  with  this  same  solution.  Moreover,  several 
of  the  quadrifids,  which  were  before  empty,  now  con- 
tained moderately  sized  or  very  small,  more  or  less 
aggregated,  globules  of  yellowish  matter,  as  likewise 
occurs  under  the  same  circumstances  with  Utricularia. 
Some  of  the  points  on  the  infolded  margins  of  the 
lobes  were  similarly  affected ; for  their  lining  of  proto- 
plasm was  a little  shrunk  and  included  yellowish 
specks  ; and  those  which  were  before  empty  now  con- 
tained small  spheres  and  irregular  masses  of  hyaline 
matter,  more  or  less  aggregated;  so  that  both  the 
points  on  the  margins  and  the  quadrifids  had  absorbed 
matter  from  the  solution  in  the  course  of  24  hrs. ; but 
to  this  subject  I shall  recur.  In  another  rather  old 
leaf,  to  which  nothing  had  been  given,  but  which  had 
been  kept  in  foul  water,  some  of  the  quadrifids  con- 
tained aggregated  translucent  globules.  These  were 
not  acted  on  by  a solution  of  one  part  of  carbonate 
of  ammonia  to  218  of  water  ; and  this  negative  result 


328 


ALDROVANDA  VESICULOSA. 


Chap.  XIV 


agrees  with  what  I have  observed  under  similar  cir- 
stances  with  TJtricularia. 

Aldrovanda  vesiculosa,  var.  australis, — Dried  leaves  of 
this  plant  from  Queensland  in  Australia  were  sent 
me  by  Prof.  Oliver  from  the  herbarium  at  Kew. 
Whether  it  ought  to  be  considered  as  a distinct  species 
or  a variety,  cannot  be  told  until  the  flowers  are  ex- 
amined by  a botanist.  The  projections  at  the  upper 
end  of  the  petiole  (from  four  to  six  in  number)  are 
considerably  longer  relatively  to  the  blade,  and  much 
more  attenuated  than  those  of  the  European  form. 
They  are  thickly  covered  for  a considerable  space 
near  their  extremities  with  the  upcurved  prickles, 
which  are  quite  absent  in  the  latter  form ; and  they 
generally  bear  on  their  tips  two  or  three  straight 
prickles  instead  of  one.  The  bilobed  leaf  appears 
also  to  be  rather  larger  and  somewhat  broader,  with 
the  pedicel  by  which  it  is  attached  to  the  upper  end 
of  the  petiole  a little  longer.  The  points  on  the 
infolded  margins  likewise  differ ; they  have  narrower 
bases,  and  are  more  pointed;  long  and  short  points 
also  alternate  with  much  more  regularity  than  in  the 
European  form.  The  glands  and  sensitive  hairs  are 
similar  in  the  two  forms.  No  quadrifid  processes 
could  be  seen  on  several  of  the  leaves,  but  I do  not 
doubt  that  they  were  present,  though  indistinguish- 
able from  their  delicacy  and  from  having  shrivelled ; 
for  they  were  quite  distinct  on  one  leaf  under  circum- 
stances presently  to  be  mentioned. 

Some  of  the  closed  leaves  contained  no  prey,  but  in 
one  there  was  a rather  large  beetle,  which  from  its 
flattened  tibiae  I suppose  was  an  aquatic  species,  but 
was  not  allied  to  Colymbetes.  All  the  softer  tissues 
of  this  beetle  were  completely  dissolved,  and  its  chiti- 
nous  integuments  were  as  clean  as  if  they  had  been 


Chap.  XIV. 


ALDROVANDA  VESICULOSA. 


329 


boiled  in  caustic  potash ; so  that  it  must  have  been 
enclosed  for  a considerable  time.  The  glands  were 
browner  and  more  opaque  than  those  on  other  leaves 
which  had  caught  nothing;  and  the  quadrifid  pro- 
cesses, from  being  partly  filled  with  brown  granular 
matter,  could  be  plainly  distinguished,  which  was  not 
the  case,  as  already  stated,  on  the  other  leaves.  Some 
of  the  points  on  the  infolded  margins  likewise  con- 
tained brownish  granular  matter.  We  thus  gain 
additional  evidence  that  the  glands,  the  quadrifid  pro- 
cesses, and  the  marginal  points,  all  have  the  power  of 
absorbing  matter,  though  probably  of  a different 
nature. 

Within  another  leaf  disintegrated  remnants  of  a 
rather  small  animal,  not  a crustacean,  which  had 
simple,  strong,  opaque  mandibles,  and  a large  unarti- 
culated chitinous  coat,  were  present.  Lumps  of  black 
organic  matter,  possibly  of  a vegetable  nature,  were 
enclosed  in  two  other  leaves;  but  in  one  of  these 
there  was  also  a small  worm  much  decayed.  But  the 
nature  of  partially  digested  and  decayed  bodies,  which 
have  been  pressed  flat,  long  dried,  and  then  soaked  in 
water,  cannot  be  recognised  easily.  All  the  leaves 
contained  unicellular  and  other  Algae,  still  of  a green- 
ish colour,  which  had  evidently  lived  as  intruders,  in 
the  same  manner  as  occurs,  according  to  Cohn,  within 
the  leaves  of  this  plant  in  Germany. 

Aldrovanda  vesiculosa,  var.  verticillata. — Dr.  King, 
Superintendent  of  the  Botanic  Gardens,  kindly  sent 
me  dried  specimens  collected  near  Calcutta.  This 
form  was,  I believe,  considered  by  Wallich  as  a distinct 
species,  under  the  name  of  verticillata.  It  resembles 
the  Australian  form  much  more  nearly  than  the  Euro- 
pean ; namely  in  the  projections  at  the  upper  end  of 
the  petiole  being  much  attenuated  and  covered  with 


330 


ALDROVANDA  VESICULOSA. 


Chap.  XIV. 


upcurved  prickles ; they  terminate  also  in  two  straight 
little  prickles.  The  bilobed  leaves  are,  I believe, 
larger  and  certainly  broader  even  than  those  of  the 
Australian  form ; so  that  the  greater  convexity  of 
their  margins  was  conspicuous.  The  length  of  an  open 
leaf  being  taken  at  100,  the  breadth  of  the  Bengal 
form  is  nearly  173,  of  the  Australian  form  147,  and 
of  the  German  134.  The  points  on  the  infolded 
margins  are  like  those  in  the  Australian  form.  Of  the 
few  leaves  which  were  examined,  three  contained 
entomostracan  crustaceans. 

Concluding  BemarJcs. — The  leaves  of  the  three  fore- 
going closely  allied  species  or  varieties  are  manifestly 
adapted  for  catching  living  creatures.  With  respect 
to  the  functions  of  the  several  parts,  there  can  be  little 
doubt  that  the  long  jointed  hairs  are  sensitive,  like 
those  of  Dionsea,  and  that,  when  touched,  they  cause 
the  lobes  to  close.  That  the  glands  secrete  a true 
digestive  fluid  and  afterwards  absorb  the  digested 
matter,  is  highly  probable  from  the  analogy  of  Dio- 
naea, — from  the  limpid  fluid  within  their  cells  being 
aggregated  into  spherical  masses,  after  they  had 
absorbed  an  infusion  of  raw  meat, — from  their  opaque 
and  granular  condition  in  the  leaf,  which  had  enclosed 
a beetle  for  a long  time, — and  from  the  clean  con- 
dition of  the  integuments  of  this  insect,  as  well  as 
of  crustaceans  (as  described  by  Cohn),  which  have 
been  long  captured.  Again,  from  the  effect  produced 
on  the  quadrifid  processes  by  an  immersion  for  24  hrs. 
in  a solution  of  urea, — from  the  presence  of  brown 
granular  matter  within  the  quadrifids  of  the  leaf  in 
which  the  beetle  had  been  caught, — and  from  the 
analogy  of  Utricularia, — it  is  probable  that  these  pro- 
cesses absorb  excrementitious  and  decaying  animal 
matter.  It  is  a more  curious  fact  that  the  points  on 


Chap.  XIV. 


CONCLUDING  REMARKS. 


331 


the  infolded  margins  apparently  serve  to  absorb  de- 
cayed animal  matter  in  the  same  manner  as  the  quad- 
rifids.  We  can  thus  understand  the  meaning  of  the 
infolded  margins  of  the  lobes  furnished  with  delicate 
points  directed  inwards,  and  of  the  broad,  flat,  outer 
portions,  bearing  quadrifid  processes ; for  these  sur- 
faces must  be  liable  to  be  irrigated  by  foul  water 
flowing  from  the  concavity  of  the  leaf  when  it  con- 
tains dead  animals.  This  would  follow  from  various 
causes, — from  the  gradual  contraction  of  the  concavity, 
— ^from  fluid  in  excess  being  secreted, — and  from  the 
generation  of  bubbles  of  air.  More  observations  are 
requisite  on  this  head ; but  if  this  view  is  correct,  we 
have  the  remarkable  case  of  different  parts  of  the 
same  leaf  serving  for  very  different  purposes — one 
part  for  true  digestion,  and  another  for  the  absorption 
of  decayed  animal  matter.  We  can  thus  also  under- 
stand how,  by  the  gradual  loss  of  either  power,  a plant 
might  be  gradually  adapted  for  the* one  function  to 
the  exclusion  of  the  other ; and  it  will  hereafter  be 
shown  that  two  genera,  namely  Pinguicula  and  Utri- 
cularia,  belonging  to  the  same  family,  have  been 
adapted  for  these  two  different  functions. 


332 


DROSOPHYLLUM  LUSITANICUM. 


Chap.  XY. 


CHAPTEE  XV. 

Dkosophyllum  — Roridula — Byblis  — Glandular  Hairs  of  other 
Plants  — Concluding  Remarks  on  the  DROSERACEiE. 

Drosophyllum  — Structure  of  leaves — Nature  of  the  secretion — Man- 
ner of  catching  insects — Power  of  absorption — Digestion  of  animal 
substances  — Summary  on  Drosophyllum  — Roridula  — Byblis  — 
Glandular  hairs  of  other  plants,  their  power  of  absorption  — Saxi- 
fraga  — Primula  — Pelargonium  — Erica  — Mirabilis  — Nicotiana 
— Summary  on  glandular  hairs  — Concluding  remarks  on  the  Dro- 
seracese. 

Drosophyllum  lusitanicum. — This  rare  plant  has 
been  found  only  in  Portugal,  and,  as  I hear  from 
Dr.  Hooker,  in  Morocco.  I obtained  living  specimens 
through  the  great  kindness  of  Mr.  W.  C.  Tait,  and 
afterwards  from  Mr.  G.  Maw  and  Dr.  Moore.  Mr.  Tait 
informs  me  that  it  grows  plentifully  on  the  sides  of 
dry  hills  near  Oporto,  and  that  vast  numbers  of  flies 
adhere  to  the  leaves.  This  latter  fact  is  well  known 
to  the  villagers,  who  call  the  plant  the  ^^fly-catcher,” 
and  hang  it  up  in  their  cottages  for  this  purpose.  A 
plant  in  my  hot-house  caught  so  many  insects  during 
the  early  part  of  April,  although  the  weather  was 
cold  and  insects  scarce,  that  it  must  have  been  in 
some  manner  strongly  attractive  to  them.  On  four 
leaves  of  a young  and  small  plant,  8,  10,  14,  and 
16  minute  insects,  chiefly  Diptera,  were  found  in  the 
autumn  adhering  to  them.  I neglected  to  examine 
the  roots,  but  I hear  from  Dr.  Hooker  that  they  are 
very  small,  as  in  the  case  of  the  previously  men- 
tioned members  of  the  same  family  of  the  Droseraceae. 
The  leaves  arise  from  an  almost  woody  axis ; they 


Chap.  XV. 


STRUCTURE  OF  LEAVES. 


333 


are  linear,  much  attenuated  towards  .their  tips,  and 
several  inches  in  length.  The  upper  surface  is  con- 
cave, the  lower  convex,  with  a narrow  channel  down 
the  middle.  Both  surfaces,  with  the  exception  of  the 
channel,  are  covered  with  glands,  supported  on  pedicels 
and  arranged  in  irregular  longitudinal  rows.  These 
organs  I shall  call  tentacles,  from  their  close  resem- 
blance to  those  of  Drosera,  though  they  have  no  power 
of  movement.  Those  on  the  same  leaf  differ  much  in 
length.  The  glands  also  differ  in  size,  and  are  of  a 
bright  pink  or  of  a purple  colour;  their  upper  sur- 
faces are  convex,  and  the  lower  flat  or  even  concave, 
so  that  they  resemble  miniature  mushrooms  in  appear- 
ance. They  are  formed  of  two  (as  I believe)  layers 
of  delicate  angular  cells,  enclosing  eight  or  ten  larger 
cells  with  thicker,  zigzag  walls.  Within  these  larger 
cells  there  are  others  marked  by  spiral  lines,  and 
apparently  connected  with  the  spiral 
vessels  which  run  up  the  green  multi- 
cellular pedicels.  The  glands  secrete 
large  drops  of  viscid  secretion.  Other 
gla-nds,  having  the  same  general 
appearance,  are  found  on  the  flower- 
peduncles  and  calyx. 

Besides  the  glands  which  are  borne 
on  longer  or  shorter  pedicels,  there 
are  numerous  ones,  both  on  the  upper 
and  lower  surfaces  of  the  leaves,  so 
small  as  to  be  scarcely  visible  to  the 
naked  eye.  They  are  colourless  and 
almost  sessile,  either  circular  or  oval 
in  outline  ; the  latter  occurring  chiefly 
on  the  backs  of  the  leaves  (fig.  14). 

Internally  they  have  exactly  the  same  structure  as 
the  larger  glands  which  are  supported  on  pedicels; 


Fig.  14. 

(^Drosophyllum  lusi- 
tanicum.) 

Part  of  leaf,  enlarged 
seven  times,  show- 
ing lower  surfai  e. 


334 


DKOSOPHYLLUM  LUSITANICUM. 


Chap.  XV. 


and  indeed  the  two  sets  almost  graduate  into  one 
another.  But  the  sessile  glands  differ  in  one  im- 
portant respect,  for  they  never  secrete  spontaneously, 
as  far  as  I have  seen,  though  I have  examined 
them  under  a high  power  on  a hot  day,  whilst 
the  glands  on  pedicels  were  secreting  copiously. 
Nevertheless,  if  little  bits  of  damp  albumen  or  fibrin 
are  placed  on  these  sessile  glands,  they  begin  after  a 
time  to  secrete,  in  the  same  manner  as  do  the  glands 
of  Dionaea  when  similarly  treated.  When  they  were 
merely  rubbed  with  a bit  of  raw  meat,  I believe  that 
they  likewise  secreted.  Both  the  sessile  glands  and 
the  taller  ones  on  pedicels  have  the  power  of  rapidly 
absorbing  nitrogenous  matter. 

The  secretion  from  the  taller  glands  differs  in  a 
remarkable  manner  from  that  of  Drosera,  in  being  acid 
before  the  glands  have  been  in  any  way  excited ; and 
judging  from  the  changed  colour  of  litmus  paper,  more 
strongly  acid  than  that  of  Drosera.  This  fact  was 
observed  repeatedly ; on  one  occasion  I chose  a young 
leaf,  which  was  not  secreting  freely,  and  had  never 
caught  an  insect,  yet  the  secretion  on  all  the  glands 
coloured  litmus  paper  of  a bright  red.  From  the 
quickness  with  which  the  glands  are  able  to  obtain 
animal  matter  from  such  substances  as  well-washed 
fibrin  and  cartilage,  I suspect  that  a small  quantity  of 
the  proper  ferment  must  be  present  in  the  secretion 
before  the  glands  are  excited,  so  that  a little  animal 
matter  is  quickly  dissolved. 

Owing  to  the  nature  of  the  secretion  or  to  the  shape 
of  the  glands,  the  drops  are  removed  from  them  with 
singular  facility.  It  is  even  somewhat  difficult,  by 
the  aid  of  a finely  pointed  polished  needle,  slightly 
damped  with  water,  to  place  a minute  particle  of  any 
kind  on  one  of  the  drops;  for  on  withdrawing  the 


Chap.  XV. 


SECRETION. 


335 


needle,  the  drop  is  generally  withdrawn ; whereas  with 
Drosera  there  is  no  such  difficulty,  though  the  drops 
are  occasionally  withdrawn.  From  this  peculiarity, 
when  a small  insect  alights  on  a leaf  of  Drosophyllum, 
the  drops  adhere  to  its  wings,  feet,  or  body,  and  are 
drawn  from  the  gland ; the  insect  then  crawls  onward 
and  other  drops  adhere  to  it;  so  that  at  last,  bathed 
by  the  viscid  secretion,  it  sinks  down  and  dies,  resting 
on  the  small  sessile  glands  with  which  the  surface  of 
the  leaf  is  thickly  covered.  In  the  case  of  Drosera, 
an  insect  sticking  to  one  or  more  of  the  exterior 
glands  is  carried  by  their  movement  to  the  centre  of 
the  leaf;  with  Drosophyllum,  this  is  effected  by  the 
crawling  of  the  insect,  as  from  its  wings  being  clogged 
by  the  secretion  it  cannot  fly  away. 

There  is  another  difference  in  function  between  the 
glands  of  these  two  plants : we  know  that  the  glands 
of  Drosera  secrete  more  copiously  when  properly 
excited.  But  when  minute  particles  of  carbonate  of 
ammonia,  drops  of  a solution  of  this  salt  or  of  the 
nitrate  of  ammonia,  saliva,  small  insects,  bits  of  raw 
or  roast  meat,  albumen,  fibrin  or  cartilage,  as  well  as 
inorganic  particles,  were  placed  on  the  glands  of  Dro- 
sophyllum, the  amount  of  secretion  never  appeared  to 
be  in  the  least  increased.  As  insects  do  not  commonly 
adhere  to  the  taller  glands,  but  withdraw  the  secretion, 
we  can  see  that  there  would  be  little  use  in  their 
having  acquired  the  habit  of  secreting  copiously  when 
stimulated ; whereas  with  Drosera  this  is  of  use,  and 
the  habit  has  been  acquired.  Nevertheless,  the  glands 
of  Drosophyllum,  without  being  stimulated,  continu- 
ally secrete,  so  as  to  replace  the  loss  by  evaporation. 
Thus  when  a plant  was  placed  under  a small  bell- 
glass  with  its  inner  surface  and  support  thoroughly 
wetted,  there  was  no  loss  by  evaporation,  and  so  much 


336  DROSOPHYLLUM  LUSITANICUM.  Chap.  XV. 

secretion  was  accumulated  in  the  course  of  a day  that 
it  ran  down  the  tentacles  and  covered  large  spaces  of 
the  leaves. 

The  glands  to  which  the  above  named  nitrogenous 
substances  and  liquids  were  given  did  not,  as  just 
stated,  secrete  more  copiously;  on  the  contrary,  they 
absorbed  their  own  drops  of  secretion  with  surprising 
quickness.  Bits  of  damp  fibrin  were  placed  on  five 
glands,  and  when  they  were  looked  at  after  an  interval 
of  1 hr.  12  m.,  the  fibrin  was  almost  dry,  the  secre- 
tion having  been  all  absorbed.  So  it  was  with  three 
cubes  of  albumen  after  1 hr.  19  m.,and  with  four  other 
cubes,  though  these  latter  were  not  looked  at  until 
2 hrs.  15  m.  had  elapsed.  The  same  result  followed 
in  between  1 hr.  15  m.  and  1 hr.  30  m.  when  particles 
both  of  cartilage  and  meat  were  placed  on  several 
glands.  Lastly,  a minute  drop  (about  of  a minim) 
of  a solution  of  one  part  of  nitrate  of  ammonia  to 
146  of  water  was  distributed  between  the  secretion 
surrounding  three  glands,  so  that  the  amount  of  fluid 
surrounding  each  was  slightly  increased ; yet  when 
looked  at  after  2 hrs.,  all  three  were  dry.  On  the 
other  hand,  seven  particles  of  glass  and  three  of  coal- 
cinders,  of  nearly  the  same  size  as  those  of  the  above 
named  organic  substances,  were  placed  on  ten  glands ; 
some  of  them  being  observed  for  18  hrs.,  and  others 
for  two  or  three  days ; but  there  was  not  the  least 
sign  of  the  secretion  being  absorbed.  Hence,  in  the 
former  cases,  the  absorption  of  the  secretion  must 
have  been  due  to  the  presence  of  some  nitrogenous 
matter,  which  was  either  already  soluble  or  was  ren- 
dered so  by  the  secretion.  As  the  fibrin  was  pure, 
and  had  been  well  washed  in  distilled  water  after 
being  kept  in  glycerine,  and  as  the  cartilage  had  been 
soaked  in  water,  I suspect  that  these  substances  must 


Chap.  XV. 


ABSOKPTION. 


337 


have  been  slightly  acted  on  and  rendered  soluble 
within  the  above  stated  short  periods. 

The  glands  have  not  only  the  power  of  rapid  absorp- 
tion, but  likewise  of  secreting  again  quickly  ; and  this 
latter  habit  has  perhaps  been  gained,  inasmuch  as 
insects,  if  they  touch  the  glands,  generally  withdraw  the 
drops  of  secretion,  which  have  to  be  restored.  The  exact 
period  of  re-secretion  was  recorded  in  only  a few  cases. 
The  glands  on  which  bits  of  meat  were  placed,  and  which 
were  nearly  dry  after  about  1 hr.  30  m.,  when  looked 
at  after  22  additional  hours,  were  found  secreting ; so 
it  was  after  24  hrs.  with  one  gland  on  which  a bit 
of  albumen  had  been  placed.  The  three  glands  to 
which  a minute  drop  of  a solution  of  nitrate  of 
ammonia  was  distributed,  and  which  became  dry  after 
2 hrs.,  were  beginning  to  re-secrete  after  only  12  addi- 
tional hours. 

Tentacles  Incajpahle  of  Movement. — Many  of  the  tall 
tentacles,  with  insects  adhering  to  them,  were  care- 
fully observed ; and  fragments  of  insects,  bits  of  raw 
meat,  albumen,  &c.,  drops  of  a solution  of  two  salts 
of  ammonia  and  of  saliva,  were  placed  on  the  glands 
of  many  tentacles ; but  not  a trace  of  movement  could 
ever  be  detected.  I also  repeatedly  irritated  the 
glands  with  a needle,  and  scratched  and  pricked  the 
blades,  but  neither  the  blade  nor  the  tentacles  became 
at  all  inflected.  We  may  therefore  conclude  that 
they  are  incapable  of  movement. 

On  . the  Power  of  Absorption  'possessed  by  the  Glands. — 
It  has  already  been  indirectly  shown  that  the  glands 
on  pedicels  absorb  animal  matter ; and  this  is  further 
shown  by  their  changed  colour,  and  by  the  aggregation 
of  their  contents,  after  they  have  been  left  in  contact 
with  nitrogenous  substances  or  liquids.  The  following 
observations  apply  both  to  the  glands  supported  on 


338 


DROSOPHYLLXJM  LUSITANICUM. 


Chap.  XV. 


pedicels  and  to  the  minute  sessile  ones.  Before  a 
gland  has  been  in  any  way  stimulated,  the  exterior  cells 
commonly  contain  only  limpid  purple  fluid ; the  more 
central  ones  including  mulberry-like  masses  of  purple 
granular  matter.  A leaf  was  placed  in  a little  solution 
of  one  part  of  carbonate  of  ammonia  to  146  of  water  (3 
grs.  to  1 oz.),  and  the  glands  were  instantly  darkened 
and  very  soon  became  black ; this  change  being  due 
to  the  strongly  marked  aggregation  of  their  contents, 
more  especially  of  the  inner  cells.  Another  leaf  was 
placed  in  a solution  of  the  same  strength  of  nitrate  of 
ammonia,  and  the  glands  were  slightly  darkened  in 
25  m.,  more  so  in  50  m.,  and  after  1 hr.  30  m.  were  of 
so  dark  a red  as  to  appear  almost  black.  Other  leaves 
were  placed  in  a weak  infusion  of  raw  meat  and  in 
human  saliva,  and  the  glands  were  much  darkened  in 
25  m.,  and  after  40  m.  were  so  dark  as  almost  to 
deserve  to  be  called  black.  Even  immersion  for  a 
whole  day  in  distilled  water  occasionally  induces  some 
aggregation  within  the  glands,  so  that  they  become  of 
a darker  tint.  lit  all  these  cases  the  glands  are 
affected  in  exactly  the  same  manner  as  those  of 
Drosera.  Milk,  however,  which  acts  so  energetically 
on  Drosera,  seems  rather  less  effective  on  Droso- 
phyllum,  for  the  glands  were  only  slightly  darkened 
by  an  immersion  of  1 hr.  20  m.,  but  became  decidedly 
darker  after  3 hrs.  Leaves  which  had  been  left  for 
7 hrs.  in  an  infusion  of  raw  meat  or  in  saliva  were 
placed  in  the  solution  of  carbonate  of  ammonia,  and 
the  glands  now  became  greenish;  whereas,  if  they 
had  been  first  placed  in  the  carbonate,  they  would 
have  become  black.  In  this  latter  case,  the  ammonia 
probably  combines  with  the  acid  of  the  secretion, 
and  therefore  does  not  act  on  the  colouring  matter  ; 
but  when  the  glands  are  first  subjected  to  an  organic 


Chap.  XV. 


DIGESTION. 


339 


fluid,  either  the  acid  is  consumed  in  the  work  of  di- 
gestion or  the  cell-walls  are  rendered  more  permeable, 
so  that  the  undecomposed  carbonate  enters  and  acts 
on  the  colouring  matter.  If  a particle  of  the  dry 
carbonate  is  placed  on  a gland,  the  purple  colour  is 
quickly  discharged,  owing  probably  to  an  excess  of  the 
salt.  The  gland,  moreover,  is  killed. 

Turning  now  to  the  action  of  organic  substances, 
the  glands  on  which  bits  of  raw  meat  were  placed 
became  dark-coloured  ; and  in  18  hrs.  their  con- 
tents were  conspicuously  aggregated.  Several  glands 
with  bits  of  albumen  and  fibrin  were  darkened  in 
between  2 hrs.  and  3 hrs. ; but  in  one  case  the 
purple  colour  was  completely  discharged.  Some 
glands  which  had  caught  flies  were  compared  with 
others  close  by ; and  though  they  did  not  differ  much 
in  colour,  there  was  a marked  difference  in  their  state 
of  aggregation.  In  some  few  instances,  however,  there 
was  no  such  difference,  and  this  appeared  to  be  due 
to  the  insects  having  been  caught  long  ago,  so  that 
the  glands  had  recovered  their  pristine  state.  In  one 
case,  a group  of  the  sessile  colourless  glands,  to  which 
a small  fly  adhered,  presented  a peculiar  appearance ; 
for  they  had  become  purple,  owing  to  purple  granular 
matter  coating  the  cell-walls.  I may  here  mention 
as  a caution  that,  soon  after  some  of  my  plants  arrived 
in  the  spring  from  Portugal,  the  glands  were  not 
plainly  acted  on  by  bits  of  meat,  or  insects,  or  a 
solution  of  ammonia — a circumstance  for  which  I 
cannot  account. 

Digestion  of  Solid  Animal  Matter,  — Whilst  I was 
trying  to  place  on  two  of  the  taller  glands  little  cubes 
of  albumen,  these  slipped  down,  and,  besmeared  with 
secretion,  were  left  resting  on  some  of  the  small  sessile 
glands.  After  24  hrs.  one  of  these  cubes  was  found 


340 


DROSOPHYLLUM  LUSITANICUM. 


Chap.  XV. 


completely  liquefied,  but  with  a few  white  streaks 
still  visible ; the  other  was  much  rounded,  but  not 
quite  dissolved.  Two  other  cubes  were  left  on  tall 
glands  for  2 hrs.  45  m.,  by  which  time  all  the  secre- 
tion was  absorbed;  but  they  were  not  perceptibly 
acted  on,  though  no  doubt  some  slight  amount  of 
animal  matter  had  been  absorbed  from  them.  They 
were  then  placed  on  the  small  sessile  glands,  which 
being  thus  stimulated  secreted  copiously  in  the 
course  of  7 hrs.  One  of  these  cubes  was  much 
liquefied  within  this  short  time ; and  both  were  com- 
pletely liquefied  after  21  hrs.  15  m. ; the  little  liquid 
masses,  however,  still  showing  some  white  streaks. 
These  streaks  disappeared  after  an  additional  period 
of  6 hrs.  30  m. ; and  by  next  morning  (i.  e.  48  hrs. 
from  the  time  when  the  cubes  were  first  placed  on 
the  glands)  the  liquefied  matter  was  wholly  absorbed. 
A cube  of  albumen  was  left  on  another  tall  gland, 
which  first  absorbed  the  secretion  and  after  24  hrs. 
poured  forth  a fresh  supply.  This  cube,  now  sur- 
rounded by  secretion,  was  left  on  the  gland  for  an 
additional  24  hrs.,  but  was  very  little,  if  at  all,  acted 
on.  We  may,  therefore,  conclude,  either  that  the 
secretion  from  the  tall  glands  has  little  power  of  diges- 
tion, though  strongly  acid,  or  that  the  amount  poured 
forth  from  a single  gland  is  insuflScient  to  dissolve  a 
particle  of  albumen  which  within  the  same  time  would 
have  been  dissolved  by  the  secretion  from  several  of  the 
small  sessile  glands.  Owing  to  the  death  of  my  last 
plant,  I was  unable  to  ascertain  which  of  these  alter- 
natives is  the  true  one. 

Four  minute  shreds  of  pure  fibrin  were  placed, 
each  resting  on  one,  two,  or  three  of  the  taller  glands. 
In  the  course  of  2 hrs.  30  m.  the  secretion  was  all 
absorbed,  and  the  shreds  were  left  almost  dry.  They 


Chap.  XV. 


CONCLUDING  KEMARKS. 


341 


were  then  pushed  on  to  the  sessile  glands.  One  shred, 
after  2 hrs.  30  m.,  seemed  quite  dissolved,  but  this  may 
have  been  a mistake.  A second,  when  examined  after 
17  hrs.  25  m.,  was  liquefied,  but  the  liquid  as  seen 
under  the  microscope  still  contained  floating  granules 
of  fibrin.  The  other  two  shreds  were  completely 
liquefied  after  21  hrs.  30  m. ; but  in  one  of  the  drops 
a very  few  granules  could  still  be  detected.  These, 
however,  were  dissolved  after  an  additional  interval 
of  6 hrs.  30  m. ; and  the  surface  of  the  leaf  for  some 
distance  all  round  was  covered  with  limpid  fluid.  It 
thus  appears  that  Drosophyllum  digests  albumen 
and  fibrin  rather  more  quickly  than  Drosera  can; 
and  this  may  perhaps  be  attributed  to  the  acid, 
together  probably  with  some  small  amount  of  the 
ferment,  being  present  in  the  secretion,  before  the 
glands  have  been  stimulated  ; so  that  digestion  begins 
at  once. 

Concluding  Remarks, — The  linear  leaves  of  Droso- 
phyllum differ  but  slightly  from  those  of  certain 
species  of  Drosera ; the  chief  differences  being,  firstly, 
the  presence  of  minute,  almost  sessile,  glands,  which, 
like  those  of  Dionsea,  do  not  secrete  until  they  are 
excited  by  the  absorption  of  nitrogenous  matter.  But 
glands  of  this  kind  are  present  on  the  leaves  of 
Drosera  hinata,  and  appear  to  be  represented  by  the 
papillae  on  the  leaves  of  Drosera  rotundifolia.  Secondly, 
the  presence  of  tentacles  on  the  backs  of  the  leaves ; 
but  we  have  seen  that  a few  tentacles,  irregularly  placed 
and  tending  towards  abortion,  are  retained  on  the 
backs  of  the  leaves  of  Drosera  binata.  There  are 
greater  differences  in  function  between  the  two  ge- 
nera. The  most  important  one  is  that  the  tentacles 
of  Drosophyllum  have  no  power  of  movement;  this 
loss  being  partially  replaced  by  the  drops  of  viscid 


842 


ROEIDULA. 


Chap.  XV. 


secretion  being  readily  withdrawn  from  the  glands;  so 
that,  when  an  insect  comes  into  contact  with  a drop, 
it  is  able  to  crawl  away,  but  soon  touches  other  drops, 
and  then,  smothered  by  the  secretion,  sinks  down  on 
the  sessile  glands  and  dies.  Another  difference  is, 
that  the  secretion  from  the  tall  glands,  before  they 
have  been  in  any  way  excited,  is  strongly  acid,  and 
perhaps  contains  a small  quantity  of  the  proper 
ferment.  Again,  these  glands  do  not*  secrete  more 
copiously  from  being  excited  by  the  absorption  of 
nitrogenous  matter  ; on  the  contrary,  they  then  absorb 
their  own  secretion  with  extraordinary  quickness.  In 
a short  time  they  begin  to  secrete  again.  All  these 
circumstances  are  probably  connected  with  the  fact 
that  insects  do  not  commonly  adhere  to  the  glands 
with  which  they  first  come  into  contact,  though  this 
does  sometimes  occur;  and  that  it  is  chiefly  the  se- 
cretion from  the  sessile  glands  which  dissolves  animal 
matter  out  of  their  bodies. 

Eoridula. 

Eoridula  dentata. — This  plant,  a native  of  the  western 
parts  of  the  Cape  of  Good  Hope,  was  sent  to  me  in  a 
dried  state  from  Kew.  It  has  an  almost  woody  stem 
and  branches,  and  apparently  grows  to  a height  of 
some  feet.  The  leaves  are  linear,  with  their  summits 
much  attenuated.  Their  upper  and  lower  surfaces 
are  concave,  with  a ridge  in  the  middle,  and  both  are 
covered  with  tentacles,  which  differ  greatly  in  length ; 
some  being  very  long,  especially  those  on  the  tips 
of  the  leaves,  and  some  very  short.  The  glands  also 
differ  much  in  size  and  are  somewhat  elongated. 
They  are  supported  on  multicellular  pedicels. 

This  plant,  therefore,  agrees  in  several  respects  with 


Chap.  XV. 


BYBLIS. 


343 


Drosophyllum,  but  differs  in  the  following  points.  I 
could  detect  no  sessile  glands ; nor  would  these  have 
been  of  any  use,  as  the  upper  surface  of  the  leaves  is 
thickly  clothed  with  pointed,  unicellular  hairs  directed 
upwards.  The  pedicels  of  the  tentacles  do  not  include 
spiral  vessels ; nor  are  there  any  spiral  cells  within  the 
glands.  The  leaves  often  arise  in  tufts  and  are  pin- 
natifid,  the  divisions  projecting  at  right  angles  to  the 
main  linear  blade.  These  lateral  divisions  are  often 
very  short  and  bear  only  a single  terminal  tentacle, 
with  one  or  two  short  ones  on  the  sides.  No  distinct 
line  of  demarcation  can  be  drawn  between  the  pedi- 
cels of  the  long  terminal  tentacles  and  the  much 
attenuated  summits  of  the  leaves.  We  may,  indeed, 
arbitrarily  fix  on  the  point  to  which  the  spiral  vessels 
proceeding  from  the  blade  extend ; but  there  is  no 
other  distinction. 

It  was  evident  from  the  many  particles  of  dirt  stick- 
ing to  the  glands  that  they  secrete  much  viscid  matter. 
A large  number  of  insects  of  many  kinds  also  adhered 
to  the  leaves.  I could  nowhere  discover  any  signs 
of  the  tentacles  having  been  inflected  over  the  cap- 
tured insects ; and  this  probably  would  have  been  seen 
even  in  the  dried  specimens,  had  they  possessed  the 
power  of  movement.  Hence,  in  this  negative  cha- 
racter, Eoridula  resembles  its  northern  representative, 
Drosophyllum. 

Byblis. 

Byhlis  gigantea  (Western  Australia).  — A dried 
specimen,  about  18  inches  in  height,  with  a strong 
stem,  was  sent  me  from  Kew.  The  leaves  are 
some  inches  in  length,  linear,  slightly  flattened,  with 
a small  projecting  rib  on  the  lower  surface.  They 
are  covered  on  all  sides  by  glands  of  two  kinds 


344 


GLANDULAR  HAIRS, 


Chap.  XV. 


— sessile  ones  arranged  in  rows,  and  others  sup- 
ported on  moderately  long  pedicels.  Towards  the 
narrow  summits  of  the  leaves  the  pedicels  are  longer 
than  elsewhere,  and  here  equal  the  diameter  of  the 
leaf.  The  glands  are  purplish,  much  flattened,  and 
formed  of  a single  layer  of  radiating  cells,  which  in 
the  larger  glands  are  from  forty  to  fifty  in  number. 
The  pedicels  consist  of  single  elongated  cells,  with 
colourless,  extremely  delicate  walls,  marked  with  the 
finest  intersecting  spiral  lines.  Whether  these  lines 
are  the  result  of  contraction  from  the  drying  of  the 
walls,  I do  not  know,  but  the  whole  pedicel  was  often 
spirally  rolled  up.  These  glandular  hairs  are  far  more 
simple  in  structure  than  the  so-called  tentacles  of  the 
preceding  genera,  and  they  do  not  differ  essentially 
from  those  borne  by  innumerable  other  plants.  The 
flower-peduncles  bear  similar  glands.  The  most  sin- 
gular character  about  the  leaves  is  that  the  apex  is 
enlarged  into  a little  knob,  covered  with  glands,  and 
about  a third  broader  than  the  adjoining  part  of  the 
attenuated  leaf.  In  two  places  dead  flies  adhered  to 
the  glands.  As  no  instance  is  known  of  unicellular 
structures  having  any  power  of  movement,*  Byblis, 
no  doubt,  catches  insects  solely  by  the  aid  of  its 
viscid  secretion.  These  probably  sink  down  besmeared 
with  the  secretion  and  rest  on  the  small  sessile  glands, 
which,  if  we  may  judge  by  the  analogy  of  Droso- 
phyllum,  then  pour  fourth  their  secretion  and  after- 
wards absorb  the  digested  matter. 

Supjplementary  Observations  on  the  Power  of  Absorp- 
tion by  the  Glandular  Hairs  of  other  Plants. — A few 
observations  on  this  subject  may  be  here  conveniently 
introduced.  As  the  glands  of  many,  probably  of  all, 


Sachs,  ‘ Traite  do  Bot.*  3rd  edit.  1874,  p.  1026. 


<^HAP.  XV. 


THEIR  POWER  OF  ABSORPTION. 


345 


the  species  of  Droseracese  absorb  various  fluids  or 
at  least  allow  them  readily  to  enter,*  it  seemed  desir- 
able to  ascertain  how  far  the  glands  of  other  plants 
which  are  not  specially  adapted  for  capturing  insects, 
had  the  same  power.  Plants  were  chosen  for  trial 
at  hazard,  with  the  exception  of  two  species  of  saxi- 
frage, which  were  selected  from  belonging  to  a family 
allied  to  the  Droseracea©.  Most  of  the  experiments 
were  made  by  immersing  the  glands  either  in  an  in- 
fusion of  raw  meat  or  more  commonly  in  a solution  of 
carbonate  of  ammonia,  as  this  latter  substance  acts  so 
powerfully  and  rapidly  on  protoplasm.  It  seemed  also 
particularly  desirable  to  ascertain  whether  ammonia 
was  absorbed,  as  a small  amount  is  contained  in  rain- 
water. With  the  Droseracese  the  secretion  of  a viscid 
fluid  by  the  glands  does  not  prevent  their  absorbing  ; so 
that  the  glands  of  other  plants  might  excrete  super- 
fluous matter,  or  secrete  an  odoriferous  fluid  as  a 
protection  against  the  attacks  of  insects,  or  for  any  other 
purpose,  and  yet  have  the  power  of  absorbing.  I 
regret  that  in  the  following  cases  I did  not  try  whether 
the  secretion  could  digest  or  render  soluble  animal 
substances,  but  such  experiments  would  have  been 
difficult  on  account  of  the  small  size  of  the  glands 
and  the  small  amount  of  secretion.  We  shall  see  in 
the  next  chapter  that  the  secretion  from  the  glandular 
hairs  of  Pinguicula  certainly  dissolves  animal  matter. 

S txifraga  uwthrosa. — The  flower-peduncles  and  petioles  of  the 
leaves  are  clothed  with  short  hairs,  bearing  pink-coloured  glands, 
formed  of  several  polygonal  cells,  with  their  pedicels  divided  by 
partitions  into  distinct  cells,  which  are  generally  colourless,  but 
sometimes  pink.  The  glands  secrete  a yellowish  viscid  fluid,  by 


* The  distinction  between  true  clearly  understood : see  Muller’s 
absorption  and  mere  permeation,  ‘ Physiology,’  Eng.  translat.  1838, 
or  imbibition,  is  by  no  means  vol.  i:  p.  280. 


346 


GLANDULAE  HAIKS, 


Chap.  XV 


which  miniite  Diptera  are  sometimes,  though  not  often,  caught.* 
The  cells  of  the  glands  contain  bright  pink  fluid,  charged  with 
granules  or  with  globular  masses  of  pinkish  pulpy  matter.  This 
matter  must  be  protoplasm,  for  it  is  seen  to  undergo  slow  but 
incessant  changes  of  form  if  a gland  be  placed  in  a drop  of 
water  and  examined.  Similar  movements  were  observed  aftei 
glands  had  been  immersed  in  water  for  1,  3,  5, 18,  and  27  hrs. 
Even  after  this  latter  period  the  glands  retained  their  bright 
pink  colour;  and  the  protoplasm  within  their  cells  did  not 
appear  to  have  become  more  aggregated.  The  continuall/ 
changing  forms  of  the  little  masses  of  protoplasm  are  not  due  to 
the  absorption  of  water,  as  they  were  seen  in  glands  kept  dry. 

A flower-stem,  still  attached  to  a plant,  was  bent  (May  29) 
so  as  to  remain  immersed  for  23  hrs.  30  m.  in  a strong  infusion 
of  raw  meat.  The  colour  of  the  contents  of  the  glands  was 
slightly  changed,  being  now  of  a duller  and  more  purple  tint 
than  before.  The  contents  also  appeared  more  aggregated,  for 
the  spaces  between  the  little  masses  of  protoplasm  were  wider ; 
but  this  latter  result  did  not  follow  in  some  other  and  similar 
experiments.  The  masses  seemed  to  change  their  forms  more 
rapidly  than  did  those  in  water ; so  that  the  cells  had  a difier- 
ent  appearance  every  four  or  five  minutes.  Elongated  masses 
became  in  the  course  of  one  or  two  minutes  spherical;  and 
spherical  ones  drew  themselves  out  and  united  with  others. 
Minute  masses  rapidly  increased  in  size,  and  three  distinct 
ones  were  seen  to  unite.  The  movements  were,  in  short, 
exactly  like  those  described  in  the  case  of  Drosera.  The  cells 
of  the  pedicels  were  not  affected  by  the  infusion ; nor  were  they 
in  the  following  experiment. 

Another  flower-stem  was  placed  in  the  same  manner  and  for 
the  same  length  of  time  in  a solution  of  one  part  of  nitrate  of 
ammonia  to  146  of  water  (or  3 grs.  to  1 oz.),  and  the  glands 
wei  e discoloured  in  exactly  the  same  manner  as  by  the  infusion 
of  raw  meat. 

Another  flower-stem  was  immersed,  as  before,  in  a solution  of 
one  part  of  carbonate  of  ammonia  to  109  of  water.  The  glands, 
after  1 hr.  30  ra.,  were  not  discoloured,  but  after  3 hrs.  45  m. 
most  of  them  had  become  dull  purple,  some  of  them  blackish- 


* In  the  case  of  Saxifraga  tri- 
dariyliteSy  Mr.  Druce  says  (‘  Phar- 
rnaceutical  Journal,’  May  1875) 
that  he  examined  some  dozens  of 
plants,  and  in  almost  every  in- 


stance remnants  of  insects  ad- 
hered to  the  leaves.  So  it  is,  as 
I hear  from  a friend,  with  this 
plant  in  Ireland. 


Chap.  XV.  THEIR  POWER  OF  ABSORPTION. 


347 


green,  a few  being  still  unaffected.  The  little  masses  of  proto- 
plasm within  the  cells  were  seen  in  movement.  The  cells  of  the 
pedicels  were  unaltered.  The  experiment  was  repeated,  and  a 
fresh  flower-stem  was  left  for  23  hrs.  in  the  solution,  and  now  a 
great  effect  was  produced ; all  the  glands  were  much  blackened, 
and  the  previously  transparent  fluid  in  the  cells  of  the  pedicels, 
even  down  to  their  bases,  contained  spherical  masses  of  granular 
matter.  By  comparing  many  different  hairs,  it  was  evident  that 
the  glands  flrst  absorb  the  carbonate,  and  that  the  effect  thus 
produced  travels  down  the  hairs  from  cell  to  cell.  The  first 
change  which  could  be  observed  is  a cloudy  appearance  in  the 
fluid,  due  to  the  formation  of  very  fine  granules,  which  after- 
wards aggregate  into  larger  masses.  Altogether,  in  the  darken- 
ing of  the  glands,  and  in  the  process  of  aggregation  travelling 
down  the  cells  of  the  pedicels,  there  is  the  closest  resemblance 
to  what  takes  place  when  a tentacle  of  Drosera  is  immersed  in 
a weak  solution  of  the  same  salt.  The  glands,  however,  absorb 
very  much  more  slowly  than  those  of  Drosera.  Besides  the 
glandular  hairs,  there  are  star-shaped  organs  which  do  not 
appear  to  secrete,  and  which  were  not  in  the  least  affected  by 
the  above  solutions. 

Although  in  the  case  of  uninjured  flower-stems  aud  leaves 
the  carbonate  seems  to  be  absorbed  only  by  the  glands,  yet 
it  enters  a cut  surface  much  more  quickly  than  a gland.  Strips 
of  the  rind  of  a flower-stem  were  torn  off,  and  the  cells  of  the 
pedicels  were  seen  to  contain  only  colourless  transparent  fluid ; 
those  of  the  glands  including  as  usual  some  granular  matter. 
These  strips  were  then  immersed  in  the  same  solution  as  before 
(one  part  of  the  carbonate  to  109  of  water),  and  in  a few 
minutes  granular  matter  appeared  in  the  lower  cells  of  all  the 
pedicels.  The  action  invariably  commenced  (for  I tried  the 
experiment  repeatedly)  in  the  lowest  cells,  and  therefore  close 
to  the  torn  surface,  and  then  gradually  travelled  up  the  hairs 
until  it  reached  the  glands,  in  a reversed  direction  to  what 
occurs  in  uninjured  specimens.  The  glands  then  became  dis- 
coloured, and  the  previously  contained  granular  matter  was 
aggregated  into  larger  masses.  Two  short  bits  of  a flower-stem 
were  also  left  for  2 hrs.  40  m.  in  a weaker  solution  of  one  part 
of  the  carbonate  to  218  of  water;  and  in  both  specimens  the 
pedicels  of  the  hairs  near  the  cut  ends  now  contained  much 
granular  matter;  and  the  glands  were  completely  discoloured. 

Lastly,  bits  of  meat  w^ere  placed  on  some  glands  ; these  were 
examined  after  23  hrs.,  as  were  others,  which  had  apparently 
not  long  before  caught  minute  flies ; but  they  did  not  present  any 


348 


GLANDULAR  HAIRS, 


Chap.  XV. 


difference  from  the  glands  of  other  hairs.  Perhaps  there  may 
not  have  been  time  enough  for  absorption.  I think  so  as  some 
glands,  on  which  dead  flies  had  evidently  long  lain,  were  of  a 
pale  dirty  purple  colour  or  even  almost  colourless,  and  the 
granular  matter  within  them  presented  an  unusual  and  some- 
what peculiar  appearance.  That  these  glands  had  absorbed 
animal  matter  from  the  flies,  probably  by  exosmose  into  the 
viscid  secretion,  we  may  infer,  not  only  from  their  changed 
colour,  but  because,  when  placed  in  a solution  of  carbonate  of 
ammonia,  some  of  the  cells  in  their  pedicels  become  filled  with 
granular  matter ; whereas  the  cells  of  other  hairs,  which  had 
not  caught  flies,  after  being  treated  with  the  same  solution  for 
the  same  length  of  time,  contained  only  a small  quantity 
of  granular  matter.  But  more  evidence  is  necessary  before  we 
fully  admit  that  the  glands  of  this  saxifrage  can  absorb,  even 
with  ample  time  allowed,  animal  matter  from  the  minute 
insects  which  they  occasionally  and  accidentally  capture. 

Suxifraga  rotundifolia  (?). — The  hairs  on  the  flower-stems  of 
this  species  are  longer  than  those  just  described,  and  bear  pale 
brown  glands.  Many  were  examined,  and  the  cells  of  the 
pedicels  were  quite  transparent.  A bent  stem  was  immersed 
for  30  m.  in  a solution  of  one  part  of  carbonate  of  ammonia  to 
109  of  water,  and  two  or  three  of  the  uppermost  cells  in  the 
pedicels  now  contained  granular  or  aggregated  matter;  the 
glands  having  become  of  a bright  yellowish-green.  The  glands 
of  this  species  therefore  absorb  the  carbonate  much  more 
quickly  than  do  those  of  Saxifraga  umbrosa,  and  the  upper 
cells  of  the  pedicels  are  likewise  affected  much  more  quickly. 
Pieces  of  the  stem  were  cut  off  and  immersed  in  the  same 
solution ; and  now  the  process  of  aggregation  travelled  up  the 
hairs  in  a reversed  direction;  the  cells  close  to  the  cut  sur- 
faces being  first  affected. 

Primula  sinensis. — The  flower-stems,  the  upper  and  lower  sur- 
faces of  the  leaves  and  their  footstalks,  are  all  clothed  with  a 
multitude  of  longer  and  shorter  hairs.  The  pedicels  of  the 
longer  hairs  are  divided  by  transverse  partitions  into  eight  or 
nine  cells.  The  enlarged  terminal  cell  is  globular,  forming  a 
gland  which  secretes  a variable  amount  of  thick,  slightly  viscid, 
not  acid,  brownish-yellow  matter. 

A piece  of  a young  flower-stem  was  first  immersed  in  distilled 
water  for  2 hrs.  30  m.,  and  the  glandular  hairs  were  not  at  all 
affected.  Another  piece,  bearing  twenty-five  short  and  nine 
long  hairs,  was  carefully  examined.  The  glands  of  the  latter 
contained  no  solid  or  semi-solid  matter ; and  those  of  only  two 


Chap.  XV.  THEIR  POWER  OF  ABSORPTION. 


349 


of  the  twenty-five  short  hairs  contained  some  globules.  This 
piece  was  then  immersed  for  2 hrs.  in  a solution  of  one  part  of 
carbonate  of  ammonia  to  109  of  water,  and  now  the  glands  of 
the  twenty-five  shorter  hairs,  with  two  or  three  exceptions,  con- 
tained either  one  large  or  from  two  to  five  smaller  spherical 
masses  of  semi-solid  matter.  Three  of  the  glands  of  the  nine  long 
hairs  likewise  included  similar  masses.  In  a few  hairs  there 
were  also  globules  in  the  cells  immediately  beneath  the  glands. 
Looking  to  all  thirty -four  hairs,  there  could  be  no  doubt  that 
the  glands  had  absorbed  some  of  the  carbonate.  Another  piece 
was  left  for  only  1 hr.  in  the  same  solution,  and  aggregated 
matter  appeared  in  all  the  glands.  My  son  Francis  examined 
some  glands  of  the  longer  hairs,  which  contained  little  masses 
of  matter,  before  they  were  immersed  in  any  solution;  and 
these  masses  slowly  changed  their  forms,  so  that  no  doubt  they 
consisted  of  protoplasm.  He  then  irrigated  these  hairs  for  1 hr. 
15  m.,  whilst  under  the  microscope,  with  a solution  of  one  part  of 
the  carbonate  to  218  of  water ; the  glands  were  not  perceptibly 
affected,  nor  could  this  have  been  expected,  as  their  contents  were 
already  aggregated.  But  in  the  cells  of  the  pedicels  numerous, 
almost  colourless,  spheres  of  matter  appeared,  which  changed 
their  forms  and  slowly  coalesced ; the  appearance  of  the  cells 
being  thus  totally  changed  at  successive  intervals  of  time. 

The  glands  on  a young  flower-stem,  after  having  been  left 
for  2 hrs.  45  m.  in  a strong  solution  of  one  part  of  the  carbonate 
to  109  of  water,  contained  an  abundance  of  aggregated  masses, 
but  whether  generated  by  the  action  of  the  salt,  I do  not 
know.  This  piece  was  again  placed  in  the  solution,  so  that 
it  was  immersed  altogether  for  6 hrs.  15  m.,  and  now  there  was 
a great  change  ; for  almost  all  the  spherical  masses  within 
the  gland-cells  had  disappeared,  being  replaced  by  granular 
matter  of  a darker  brown.  The  experiment  was  thrice  re- 
peated with  nearly  the  same  result.  On  one  occasion  the  piece 
was  left  immersed  for  8 hrs.  30  m.,  and  though  almost  all  the 
spherical  masses  were  changed  into  the  brown  granular  matter, 
a few  still  remained.  If  the  spherical  masses  of  aggregated 
matter  had  been  originally  produced  merely  by  some  chemical 
or  physical  action,  it  seems  strange  that  a somewhat  longer 
immersion  in  the  same  solution  should  so  completely  alter 
their  character.  But  as  the  masses  which  slowly  and 
spontaneously  changed  theii*  forms  must  have  consisted  of 
living  protoplasm,  there  is  nothing  surprising  in  its  being 
injured  or  killed,  and  its  appearance  wholly  changed  by  long 
immersion  in  so  strong  a solution  of  the  carbonate  as  that 


350 


GLANDULAR  HAIRS, 


Chap.  XV. 


employed.  A solution  of  this  strength  paralyses  all  movement 
in  Drosera,  but  does  not  kill  the  protoplasm ; a still  stronger 
solution  prevents  the  protoplasm  from  aggregating  into  the 
ordinary  full-sized  globular  masses,  and  these,  though  they 
do  not  disintegrate,  become  granular  and  opaque.  In  nearly 
the  same  manner,  too  hot  water  and  certain  solutions  (for 
instance,  of  the  salts  of  soda  and  potash)  cause  at  first  an 
imperfect  kind  of  aggregation  in  the  cells  of  Drosera ; the  little 
masses  afterwards  breaking  up  into  granular  or  pulpy  brown 
matter.  All  the  foregoing  experiments  were  made  on  flower- 
stems,  but  a piece  of  a leaf  was  immersed  for  30  m.  in  a strong 
solution  of  the  carbonate  (one  part  to  109  of  water),  and  little 
globular  masses  of  matter  appeared  in  all  the  glands,  which 
before  contained  only  limpid  fluid. 

I made  also  several  experiments  on  the  action  of  the  vapour 
of  the  carbonate  on  the  glands ; but  will  give  only  a few  cases. 
The  cut  end  of  the  footstalk  of  a young  leaf  was  protected  with 
sealing-wax,  and  was  then  placed  under  a small  bell-glass,  with 
a large  pinch  of  the  carbonate.  After  10  m.  the  glands  showed 
a considerable  degree  of  aggregation,  and  the  protoplasm  lining 
the  cells  of  the  pedicels  was  a little  separated  from  the  walls. 
Another  leaf  was  left  for  50  m.  with  the  same  result,  excepting 
that  the  hairs  became  throughout  their  whole  length  of  a 
brownish  colour.  In  a third  leaf,  which  was  exposed  for  1 hr. 
50  m.,  there  was  much  aggregated  matter  in  the  glands ; and 
some  of  the  masses  showed  signs  of  breaking  up  into  brown 
granular  matter.  This  leaf  was  again  placed  in  the  vapour, 
so  that  it  was  exposed  altogether  for  5 hrs.  30  m. ; and  now, 
though  I examined  a large  number  of  glands,  aggregated 
masses  were  found  in  only  two  or  three;  in  all  the  others, 
the  masses,  which  before  had  been  globular,  were  converted 
into  brown,  opaque,  granular  matter.  We  thus  see  that 
exposure  to  the  vapour  for  a considerable  time  produces  the  same 
effects  as  long  immersion  in  a strong  solution.  In  both  cases 
there  could  hardly  be  a doubt  that  the  salt  had  been  absorbed 
chiefly  or  exclusively  by  the  glands. 

On  another  occasion  bits  of  damp  fibrin,  drops  of  a weak  in- 
fusion of  raw  meat  and  of  water,  were  left  for  24  hrs.  on  some 
leaves ; the  hairs  were  then  examined,  but  to  my  surprise  differed 
in  no  respect  from  others  which  had  not  been  touched  by  these 
fluids.  Most  of  the  cells,  however,  included  hyaline,  motionless 
little  spheres,  which  did  not  seem  to  consist  of  protoplasm, 
but,  I suppose,  of  some  balsam  or  essential  oil. 

Pelargonium  zonale  (var.  edged  with  white). — The  leaves 


Chap.  XV.  THEIR  POWER  OF  ABSORPTION, 


351 


are  clothed  with  numerous  multicellular  hairs;  some  simply 
pointed ; others  bearing  glandular  heads,  and  differing  much  in 
length.  The  glands  on  a piece  of  leaf  were  examined  and  found 
to  contain  only  limpid  fluid;  most  of  the  water  was  removed 
from  beneath  the  covering  glass,  and  a minute  drop  of  one  part 
of  carbonate  of  ammonia  to  146  of  water  was  added ; so  that  an 
extremely  small  dose  was  given.  After  an  interval  of  only  3 m. 
there  were  signs  of  aggregation  within  the  glands  of  the  shorter 
hairs ; and  after  5 m.  many  small  globules  of  a pale  brown  tint 
appeared  in  all  of  them;  similar  globules,  but  larger,  being 
found  in  the  large  glands  of  the  longer  hairs.  After  the  speci- 
men had  been  left  for  1 hr.  in  the  solution,  many  of  the  smaller 
globules  had  changed  their  positions ; and  two  or  three  vacuoles 
or  small  spheres  (for  I know  not  which  they  were)  of  a rather 
darker  tint  appeared  within  some  of  the  larger  globules. 
Little  globules  could  now  be  seen  in  some  of  the  uppermost 
cells  of  the  pedicels,  and  the  protoplasmic  lining  was  slightly 
separated  from  the  walls  of  the  lower  cells.  After  2 hrs.  30  m. 
from  the  time  of  first  immersion,  the  large  globules  within 
the  glands  of  the  longer  hairs  were  converted  into  masses  of 
darker  brown  granular  matter.  Hence  from  what  we  have  seen 
with  Primula  sinensis,  there  can  be  little  doubt  that  these 
masses  originally  consisted  of  living  protoplasm. 

A drop  of  a weak  infusion  of  raw  meat  was  placed  on  a leaf, 
and  after  2 hrs.  30  m.  many  spheres  could  be  seen  within  the 
glands.  These  spheres,  when  looked  at  again  after  30  m.,  had 
slightly  changed  their  positions  and  forms,  and  one  had  sepa- 
rated into  two ; but  the  changes  were  not  quite  like  those  which 
the  protoplasm  of  Drosera  undergoes.  These  hairs,  moreover, 
had  not  been  examined  before  immersion,  and  there  were  similar 
spheres  in  some  glands  which  had  not  been  touched  by  the 
infusion. 

Erica  tetralix, — A few  long  glandular  hairs  project  from  the 
margins  of  the  upper  surfaces  of  the  leaves.  The  pedicels  are 
formed  of  several  rows  of  cells,  and  support  rather  large  globular 
heads,  secreting  viscid  matter,  by  which  minute  insects  are 
occasionally,  though  rarely,  caught.  Some  leaves  were  left  for 
23  hrs.  in  a weak  infusion  of  raw  meat  and  in  water,  and 
the  hairs  were  then  compared,  but  they  differed  very  little  or 
not  at  all.  In  both  cases  the  contents  of  the  cells  seemed  rather 
more  granular  than  they  were  before ; but  the  granules  did  not 
exhibit  any  movement.  Other  leaves  were  left  for  23  hrs.  in  a 
solution  of  one  part  of  carbonate  of  ammonia  to  218  of  water, 
and  here  again  the  granular  matter  appeared  to  have  increased 
16 


352 


GLANDULAR  HAIRS, 


Chap.  XV. 


in  amount ; but  one  such  mass  retained  exactly  the  same  form  as 
before  after  an  interval  of  5 hrs.,  so  that  it  could  hardly  have 
consisted  of  living  protoplasm.  These  glands  seem  to  have  very 
little  or  no  power  of  absorption,  certainly  much  less  than  those 
of  the  foregoing  plants. 

Mirahilis  longiflora, — The  stems  and  both  surfaces  of  the 
leaves  bear  viscid  hairs.  Young  plants,  from  12  to  18  inches 
in  height  in  my  greenhouse,  caught  so  many  minute  Diptera, 
Coleoptera,  and  larvae,  that  they  were  quite  dusted  with  them. 
The  hairs  are  short,  of  unequal  lengths,  formed  of  a single  row 
of  cells,  surmounted  by  an  enlarged  cell  which  secretes  viscid 
matter.  These  terminal  cells  or  glands  contain  granules  and 
often  globules  of  granular  matter.  Within  a gland  which  had 
caught  a small  insect,  one  such  mass  was  observed  to  undergo 
incessant  changes  of  form,  with  the  occasional  appearance  of 
vacuoles.  But  I do  not  believe  that  this  protoplasm  had  been 
generated  by  matter  absorbed  from  the  dead  insect;  for, 
on  comparing  several  glands  which  had  and  had  not  caught 
insects,  not  a shade  of  difference  could  be  perceived  between 
them,  and  they  all  contained  fine  granular  matter.  A piece  of 
leaf  was  immersed  for  24  hrs.  in  a solution  of  one  part  of  car- 
bonate of  ammonia  to  218  of  water,  but  the  hairs  seemed  very 
little  affected  by  it,  excepting  that  perhaps  the  glands  were 
rendered  rather  more  opaque.  In  the  leaf  itself,  however,  the 
grains  of  chlorophyll  near  the  cut  surfaces  had  run  together, 
or  become  aggregated.  Nor  were  the  glands  on  another  leaf, 
after  an  immersion  for  24  hrs.  in  an  infusion  of  raw  meat,  in 
the  least  affected;  but  the  protoplasm  lining  the  cells  of  the 
pedicels  had  shrunk  greatly  from  the  walls.  This  latter  effect 
may  have  been  due  to  exosmose,  as  the  infusion  was  strong. 
We  may,  therefore,  conclude  that  the  glands  of  this  plant  either 
have  no  power  of  absorption  or  that  the  protoplasm  which  they 
contain  is  not  acted  on  by  a solution  of  carbonate  of  ammonia 
(and  this  seems  scarcely  credible)  or  by  an  infusion  of  meat. 

Nicotiana  tabacum, — This  plant  is  covered  with  innumerable 
hairs  of  unequal  lengths,  which  catch  many  minute  insects. 
The  pedicels  of  the  hairs  are  divided  by  transverse  partitions, 
and  the  secreting  glands  are  formed  of  many  cells,  containing 
greenish  matter  with  little  globules  of  some  substance.  Leaves 
were  left  in  an  infusion  of  raw  meat  and  in  water  for  26  hrs., 
but  i3i*esented  no  difference.  Some  of  these  same  leaves 
were  then  left  for  above  2 hrs.  in  a solution  of  carbonate  of 
ammonia,  but  no  effect  was  produced.  I regret  that  other 
experiments  were  not  tried  with  more  care,  as  M.  Schloesing 


Chap.  XV. 


THEIR  POWER  OF  ABSORPTION. 


353 


has  shown*  that  tobacco  plants  supplied  with  the  vapour  of 
carbonate  of  ammonia  yield  on  analysis  a greater  amount  of 
nitrogen  than  other  plants  not  thus  treated ; and,  from  what 
we  have  seen,  it  is  probable  that  some  of  the  vapour  may  be 
absorbed  by  the  glandular  hairs. 

Summary  of  the  Observations  on  Glandular  Hairs. — 
From  the  foregoing  observations,  few  as  they  are,  we 
see  that  the  glands  of  two  species  of  Saxifraga,  of  a 
Primula  and  Pelargonium,  have  the  power  of  rapid 
absorption ; whereas  the  glands  of  an  Erica,  Mirabilis, 
and  Nicotiana,  either  have  no  such  power,  or  the 
contents  of  the  cells  are  not  affected  by  the  fluids 
employed,  namely  a solution  of  carbonate  of  am- 
monia and  an  infusion  of  raw  meat.  As  the  glands 
of  the  Mirabilis  contain  protoplasm,  which  did  not 
become  aggregated  from  exposure  to  the  fluids  just 
named,  though  the  contents  of  the  cells  in  the  blade 
of  the  leaf  were  greatly  affected  by  carbonate  of 
ammonia,  we  may  infer  that  they  cannot  absorb.  We 
may  further  infer  that  the  innumerable  insects  caught 
by  this  plant  are  of  no  more  service  to  it  than  are 
those  which  adhere  to  the  deciduous  and  sticky  scales 
of  the  leaf-buds  of  the  horse-chestnut. 

The  most  interesting  case  for  us  is  that  of  the  two 
species  of  Saxifraga,  as  this  genus  is  distantly  allied 
to  Drosera.  Their  glands  absorb  matter  from  an 
infusion  of  raw  meat,  from  solutions  of  the  nitrate 
and  carbonate  of  ammonia,  and  apparently  from 
decayed  insects.  This  was  shown  by  the  changed 
dull  purple  colour  of  the  protoplasm  within  the  cells 
of  the  glands,  by  its  state  of  aggregation,  and  appa- 
rently by  its  more  rapid  spontaneous  movements. 


♦ ‘ Comptes  rendus,’  June  15,  1874.  A good  abstract  of  this  paper 
is  given  in  the  ‘Gardener's  Chronicle,*  July  11,  1874. 


354 


GLANDULAR  HAIRS. 


Chap.  XY. 


The  aggregating  process  spreads  from  the  glands 
down  the  pedicels  of  the  hairs;  and  we  may  assume 
that  any  matter  which  is  absorbed  ultimately  reaches 
the  tissues  of  the  plant.  On  the  other  hand,  the  process 
travels  up  the  hairs  whenever  a surface  is  cut  and  ex- 
posed to  a solution  of  the  carbonate  of  ammonia. 

The  glands  on  the  flower -stalks  and  leaves  of 
Primula  sinensis  quickly  absorb  a solution  of  the 
carbonate  of  ammonia,  and  the  protoplasm  which  they 
contain  becomes  aggregated.  The  process  was  seen 
in  some  cases  to  travel  from  the  glands  into  the  upper 
cells  of  the  pedicels.  Exposure  for  10  m.  to  the 
vapour  of  this  salt  likewise  induced  aggregation. 
When  leaves  were  left  from  6 hrs.  to  7 hrs.  in  a strong 
solution,  or  were  long  exposed  to  the  vapour,  the  little 
masses  of  protoplasm  became  disintegrated,  brown,  and 
granular,  and  were  apparently  killed.  An  infusion  of 
raw  meat  produced  no  effect  on  the  glands. 

The  limpid  contents  of  the  glands  of  Pelargonium 
zonale  became  cloudy  and  granular  in  from  3 m.  to  5 m. 
when  they  were  immersed  in  a weak  solution  of  the  car- 
bonate of  ammonia ; and  in  the  course  of  1 hr.  granules 
appeared  in  the  upper  cells  of  the  pedicels.  As  the 
aggregated  masses  slowly  changed  their  forms,  and  as 
they  suffered  disintegration  when  left  for  a consider- 
able time  in  a strong  solution,  there  can  be  little  doubt 
that  they  consisted  of  protoplasm.  It  is  doubtful 
whether  an  infusion  of  raw  meat  produced  any  effect. 

The  glandular  hairs  of  ordinary  plants  have  gene- 
rally been  considered  by  physiologists  to  serve  only 
as  secreting  or  excreting  organs,  but  we  now  know  that 
they  have  the  power,  at  least  in  some  cases,  of  absorbing 
both  a solution  and  the  vapour  of  ammonia.  As  rain- 
water contains  a small  percentage  of  ammonia,  and  the 
atmosphere  a minute  quantity  of  the  carbonate,  this 


Chap.  XV. 


DEOSERACEiE. 


355 


power  can  hardly  fail  to  be  beneficial.  Nor  can  the 
benefit  be  quite  so  insignificant  as  it  might  at  first  be 
thought,  for  a moderately  fine  plant  of  Primula 
sinensis  bears  the  astonishing  number  of  above  two 
millions  and  a half  of  glandular  hairs,*  all  of  which 
are  able  to  absorb  ammonia  brought  to  them  by  the 
rain.  It  is  moreover  probable  that  the  glands  of  some 
of  the  above  named  plants  obtain  animal  matter  from 
the  insects  which  are  occasionally  entangled  by  the 
viscid  secretion. 

Concluding  Kemarks  on  the  Droserace^. 

The  six  known  genera  composing  this  family  have 
now  been  described  in  relation  to  our  present  subject, 
as  far  as  my  means  have  permitted.  They  all  capture 
insects.  This  is  effected  by  Drosophyllum,  Eoridula, 
and  Byblis,  solely  by  the  viscid  fluid  secreted  from 
their  glands;  by  Drosera,  through  the  same  means, 
together  with  the  movements  of  the  tentacles ; by 
Dionaea  and  Aldrovanda,  through  the  closing  of  the 
blades  of  the  leaf.  In  these  two  last  genera  rapid 


* My  son  Francis  counted  the 
hairs  on  a space  measured  by 
means  of  a micrometer,  and  found 
that  there  were  35,336  on  a 
square  inch  of  the  upper  surface 
of  a leaf,  and  30,035  on  the  lower 
surface ; that  is,  in  about  the  pro- 
portion of  100  on  the  upper  to  85 
on  the  lower  surface.  On  a square 
inch  of  both  surfaces  there  were 
65,371  hairs.  A moderately  fine 
plant  bearing  twelve  leaves  (the 
larger  ones  being  a little  more 
than  2 inches  in  diameter)  was 
now  selected,  and  the  area  of  all 
the  leaves,  together  with  their 
foot-stalks  (the  flower-stems  not 
being  included),  was  found  by  a 


planimeter  to  be  39*285  square 
inches;  so  that  the  area  of  both 
surfaces  was  78*57  square  inches. 
Thus  the  plant  (excluding  the 
flower-stems)  must  have  borne 
the  astonishing  number  of 
2,568,099  glandular  hairs.  Tlie 
hairs  were  counted  late  in  the 
autumn,  and  by  the  following 
spring  (May)  the  leaves  of  some 
other  plants  of  the  same  lot  were 
found  to  be  from  one-third  to  on^ 
fourth  broader  and  longer  «iian 
they  were  before ; so  that  no 
doubt  the  glandular  hairs  had 
increased  in  number,  and  pro- 
bably now  much  exceeded  three 
millions. 


356 


CONCLUDING  REMARKS 


Chap.  XV. 


movement  makes  up  for  the  loss  of  viscid  secretion. 
In  every  case  it  is  some  part  of  the  leaf  which  moves. 
In  Aldrovanda  it  appears  to  be  the  basal  parts  alone 
which  contract  and  carry  with  them  the  broad,  thin 
margins  of  the  lobes.  In  Dionsea  the  whole  lobe,  with 
the  exception  of  the  marginal  prolongations  or  spikes, 
curves  inwards,  though  the  chief  seat  of  movement  is 
near  the  midrib.  In  Drosera  the  chief  seat  is  in  the 
lower  part  of  the  tentacles,  which,  homologically,  may 
be  considered  as  prolongations  of  the  leaf;  but  the 
whole  blade  often  curls  inwards,  converting  the  leaf 
into  a temporary  stomach. 

There  can  hardly  be  a doubt  that  all  the  plants 
belonging  to  these  six  genera  have  the  power  of  dis- 
solving animal  matter  by  the  aid  of  their  secretion, 
which  contains  an  acid,  together  with  a ferment 
almost  identical  in  nature  with  pepsin ; and  that  they 
afterwards  absorb  the  matter  thus  digested.  This  is 
certainly  the  case  with  Drosera,  Drosophyllum,  and 
Dionaea ; almost  certainly  with  Aldrovanda ; and,  from 
analogy,  very  probable  with  Eoridula  and  Byblis.  We 
can  thus  understand  how  it  is  that  the  three  first- 
named  genera  are  provided  with  such  small  roots,  and 
that  Aldrovanda  is  quite  rootless;  about  the  roots 
of  the  two  other  genera  nothing  is  known.  It  is,  no 
doubt,  a surprising  fact  that  a whole  group  of  plants 
(and,  as  we  shall  presently  see,  some  other  plants 
not  allied  to  the  Droseraceae)  should  subsist  partly  by 
digesting  animal  matter,  and  partly  by  decomposing 
carbonic  acid,  instead  of  exclusively  by  this  latter 
means,  together  with  the  absorption  of  matter  from 
the  soil  by  the  aid  of  roots.  We  have,  however,  an 
equally  anomalous  case  in  the  animal  kingdom ; the 
rhizocephalous  crustaceans  do  not  feed  like  other 
animals  by  their  mouths,  for  they  are  destitute  of  an 


Chap.  XV. 


ON  THE  DROSERACE^. 


357 


alimentary  canal ; but  they  live  by  absorbing  through 
root-like  processes  the  juices  of  the  animals  on  which 
they  are  parasitic.* 

Of  the  six  genera,  Drosera  has  been  incomparably 
the  most  successful  in  the  battle  for  life ; and  a large 
part  of  its  success  may  be  attributed  to  its  manner 
of  catching  insects.  It  is  a dominant  form,  for  it  is 
believed  to  include  about  100  species, f which  range  in 
the  Old  World  from  the  Arctic  regions  to  Southern 
India,  to  the  Cape  of  Good  Hope,  Madagascar,  and 
Australia;  and  in  the  New  World  from  Canada  to 
Tierra  del  Fuego.  In  this  respect  it  presents  a marked 
contrast  with  the  five  other  genera,  which  appear  to  be 
failing  groups.  Dionma  includes  only  a single  species, 
which  is  confined  to  one  district  in  Carolina.  The 
three  varieties  or  closely  allied  species  of  Aldrovanda, 
like  so  many  water-plants,  have  a wide  range  from 
Central  Europe  to  Bengal  and  Australia.  Droso- 
phyllum  includes  only  one  species,  limited  to  Portugal 
and  Morocco.  Koridula  and  Byblis  each  have  (as  I 


* Fritz  Muller,  ‘ Facts  for  Dar- 
win,’ Eng.  trans.  1869,  p.  139.  The 
rhizocephalous  crustaceans  are 
allied  to  the  cirripedes.  It  is  hardly 
possible  to  imagine  a greater  dif- 
ference than  that  between  an  ani- 
mal with  prehensile  limbs,  a well- 
constructed  mouth  and  alimentary 
canal,  and  one  destitute  of  all 
these  organs  and  feeding  by  ab- 
sorption through  branching  root- 
like processes.  If  one  rare  cirri- 
pede,  the  Anelasma  squalicola,  had 
become  extinct,  it  would  have 
been  very  difficult  to  conjecture 
how*  so  enormous  a change  could 
have  been  gradually  effected. 
But,  as  Fritz  Muller  remarks,  we 
have  in  Anelasma  an  animal  in 
an  almost  exactly  intermediate 


condition,  for  it  has  root-like  pro- 
cesses embedded  in  the  skin  of  the 
shark  on  which  it  is  parasitic,  and 
its  prehensile  cirri  and  mouth  (as 
described  in  my  monograph  on 
the  Lepadidm,  ‘Ray  Soc.’  1851, 
p.  169)  are  in  a most  feeble  and 
almost  rudimentary  condition. 
Dr.  R.  Kossmann  has  given  a very 
interesting  discussion  on  this 
subject  in  his  ‘ Suctoria  and  Le- 
padidse,’  1873.  See  also.  Dr. 
Dohrn,  ‘ Der  Ursprung  der  Wir- 
belthiere,’  1875,  p.  77. 

t Bentham  and  Hooker,  ‘ Genera 
Plan  tar  um.’  Australia  is  the  me- 
tropolis of  the  genus,  forty-one 
species  having  been  described 
from  this  country,  as  Prof.  Oliver 
informs  me. 


358 


CONCLUDING  REMAKES 


Chap.  XV. 


hear  from  Prof.  Oliver)  two  species ; the  former  con- 
fined to  the  western  parts  of  the  Cape  of  Good  Hope, 
and  the  latter  to  Australia.  It  is  a strange  fact  that 
Dionaea,  which  is  one  of  the  most  beautifully  adapted 
plants  in  the  vegetable  kingdom,  should  apparently  be 
on  the  high-road  to  extinction.  This  is  all  the  more 
strange  as  the  organs  of  Dionaea  are  more  highly 
differentiated  than  those  of  Drosera ; its  filaments 
serve  exclusively  as  organs  of  touch,  the  lobes  for 
capturing  insects,  and  the  glands,  when  excited,  for 
secretion  as  well  as  for  absorption;  whereas  with 
Drosera  the  glands  serve  all  these  purposes,  and  secrete 
without  being  excited. 

By  comparing  the  structure  of  the  leaves,  their 
degree  of  complication,  and  their  rudimentary  parts 
in  the  six  genera,  we  are  led  to  infer  that  their  common 
parent  form  partook  of  the  characters  of  Drosophyllum, 
Eoridula,  and  Byblis.  The  leaves  of  this  ancient  form 
were  almost  certainly  linear,  perhaps  divided,  and  bore 
on  their  upper  and  lower  surfaces  glands  which  had 
the  power  of  secreting  and  absorbing.  Some  of  these 
glands  were  mounted  on  pedicels,  and  others  were 
almost  sessile ; the  latter  secreting  only  when  stimu- 
lated by  the  absorption  of  nitrogenous  matter.  In 
Byblis  the  glands  consist  of  a single  layer  of  cells, 
supported  on  a unicellular  pedicel ; in  Eoridula  they 
have  a more  complex  structure,  and  are  supported  on 
pedicels  formed  of  several  rows  of  cells;  in  Droso- 
phyllum they  further  include  spiral  cells,  and  the  pedi- 
cels include  a bundle  of  spiral  vessels.  But  in  these 
three  genera  these  organs  do  not  possess  any  power  of 
movement,  and  there  is  no  reason  to  doubt  that  they 
are  of  the  nature  of  hairs  or  trichomes.  Although  in 
innumerable  instances  foliar  organs  move  when  ex- 
cited, no  case  is  known  of  a trichome  having  such 


Chap.  XV.  ON  THE  DKOSEKACE^.  359 

power.*  We  are  thus  led  to  inquire  how  the  so-called 
tentacles  of  Drosera,  which  are  manifestly  of  the  same 
general  nature  as  the  glandular  hairs  of  the  above 
three  genera,  could  have  acquired  the  power  of  moving. 
Many  botanists  maintain  that  these  tentacles  consist 
of  prolongations  of  the  leaf,  because  they  include  vas- 
cular tissue,  but  this  can  no  longer  be  considered  as  a 
trustworthy  distinctiomf  The  possession  of  the  power 
of  movement  on  excitement  would  have  been  safer 
evidence.  But  when  we  consider  the  vast  number  of 
the  tentacles  on  both  surfaces  of  the  leaves  of  Droso- 
phyllum,  and  on  the  upper  surface  of  the  leaves  of 
Drosera,  it  seems  scarcely  possible  that  each  tentacle 
could  have  aboriginally  existed  as  a prolongation  of 
the  leaf.  Eoridula,  perhaps,  shows  us  how  we  may 
reconcile  these  difficulties  with  respect  to  the  homo- 
logical  nature  of  the  tentacles.  The  lateral  divisions 
of  the  leaves  of  this  plant  terminate  in  long  tentacles ; 
and  these  include  spiral  vessels  which  extend  for  only 
a short  distance  up  them,  with  no  line  of  demarcation 
between  what  is  plainly  the  prolongation  of  the  leaf 
and  the  pedicel  of  a glandular  hair.  Therefore  there 
would  be  nothing  anomalous  or  unusual  in  the  basal 
parts  of  these  tentacles,  which  correspond  with  the 
marginal  ones  of  Drosera,  acquiring  the  power  of 
movement;  and  we  know  that  in  Drosera  it  is  only 
the  lower  part  which  becomes  inflected.  But  in  order 
to  understand  how  in  this  latter  genus  not  only  the  mar- 
ginal but  all  the  inner  tentacles  have  become  capable 
of  movement,  we  must  further  assume,  either  that 
through  the  principle  of  correlated  development  this 


* Sachs,  ‘ Traite  de  Botanique,’  hague,  1873,  p.  6.  ‘ Extrait  des 

3rd  edit.  1874,  p.  1026.  Videnskabelige  Meddelelser  de 

t Hr.  Warming,  ‘ Sur  la  Diffe-  la  Soc.  d’  Hist.  nat.  de  Copen 
rence  entre  les  Trichomes,’  Copen-  hague,^  Nos.  10-12,  1872. 


360 


CONCLUDING  REMARKS 


Chap.  XV, 


power  was  transferred  to  the  basal  parts  of  the  hairs, 
or  that  the  surface  of  the  leaf  has  been  prolonged 
upwards  at  numerous  points,  so  as  to  unite  with  the 
hairs,  thus  forming  the  bases  of  the  inner  tentacles. 

The  above  named  three  genera,  namely  Droso- 
phyllum,  Eoridula,  and  Byblis,  which  appear  to  have 
retained  a primordial  condition,  still  bear  glandular 
hairs  on  both  surfaces  of  their  leaves ; but  those  on 
the  lower  surface  have  since  disappeared  in  the  more 
highly  developed  genera,  with  the  partial  exception 
of  one  species,  Drosera  binata.  The  small  sessile 
glands  have  also  disappeared  in  some  of  the  genera, 
being  replaced  in  Eoridula  by  hairs,  and  in  most 
species  of  Drosera  by  absorbent  papillae.  Drosera 
hinatay  with  its  linear  and  bifurcating  leaves,  is  in 
an  intermediate  condition.  It  still  bears  some  sessile 
glands  on  both  surfaces  of  the  leaves,  and  on  the  lower 
surface  a few  irregularly  placed  tentacles,  which  are 
incapable  of  movement.  A further  slight  change 
would  convert  the  linear  leaves  of  this  latter  species 
into  the  oblong  leaves  of  Drosera  anglica,  and  these 
might  easily  pass  into  orbicular  ones  with  footstalks, 
like  those  of  Drosera  rotundifolia.  The  footstalks  of  this 
latter  species  bear  multicellular  hairs,  which  we  have 
good  reason  to  believe  represent  aborted  tentacles. 

The  parent  form  of  Dionaea  and  Aldrovanda  seems  to 
have  been  closely  allied  to  Drosera,  and  to  have  had 
rounded  leaves,  supported  on  distinct  footstalks,  and 
furnished  with  tentacles  all  round  the  circumference, 
with  other  tentacles  and  sessile  glands  on  the  upper 
surface.  I think  so  because  the  marginal  spikes  of 
Dionaea  apparently  represent  the  extreme  marginal 
tentacles  of  Drosera,  the  six  (sometimes  eight)  sensitive 
filaments  on  the  upper  surface,  as  well  as  the  more 
numerous  ones  in  Aldrovanda,  representing  the  central 


Chap.  XV. 


ON  THE  DROSEEACEiE. 


361 


tentacles  of  Drosera,  with  their  glands  aborted,  but  their 
sensitiveness  retained.  Under  this  point  of  view  we 
should  bear  in  mind  that  the  summits  of  the  tentacles 
of  Drosera,  close  beneath  the  glands,  are  sensitive. 

The  three  most  remarkable  characters  possessed  by 
the  several  members  of  the  Droseracese  consist  in  the 
leaves  of  some  having  the  power  of  movement  when 
excited,  in  their  glands  secreting  a fluid  which  digests 
animal  matter,  and  in  their  absorption  of  the  digested 
matter.  Can  any  light  be  thrown  on  the  steps 
by  which  these  remarkable  powers  were  gradually 
acquired  ? 

As  the  walls  of  the  cells  are  necessarily  permeable 
to  fluids,  in  order  to  allow  the  glands  to  secrete,  it  is 
not  surprising  that  they  should  readily  allow  fluids  to 
pass  inwards ; and  this  inward  passage  would  deserve 
to  be  called  an  act  of  absorption,  if  the  fluids  com- 
bined with  the  contents  of  the  glands.  J udging  from 
the  evidence  above  given,  the  secreting  glands  of 
many  other  plants  can  absorb  salts  of  ammonia,  of 
which  they  must  receive  small  quantities  from  the  rain. 
This  is  the  case  with  two  species  of  Saxifraga,  and  the 
glands  of  one  of  them  apparently  absorb  matter  from 
captured  insects,  and  certainly  from  an  infusion  of  raw 
meat.  There  is,  therefore,  nothing  anomalous  in  the 
Droserace80  having  acquired  the  power  of  absorption 
in  a much  more  highly  developed  degree. 

It  is  a far  more  remarkable  problem  how  the 
members  of  this  family,  and  Pinguicula,  and,  as  Dr. 
Hooker  has  recently  shown.  Nepenthes,  could  all  have 
acquired  the  power  of  secreting  a fluid  which  dis- 
solves or  digests  animal  matter.  The  six  genera  of 
the  Droseracese  have  probably  inherited  this  power 
from  a common  progenitor,  but  this  cannot  apply  to 


362 


CONCLUDING  EEMARKS 


Chap.  XV. 


Pinguicula  or  Nepenthes,  for  these  plants  are  not  at  all 
closely  related  to  the  Droseraceae.  But  the  diflSculty 
is  not  nearly  so  great  as  it  at  first  appears.  Firstly,  the 
juices  of  many  plants  contain  an  acid,  and,  apparently, 
any  acid  serves  for  digestion.  Secondly,  as  Dr.  Hooker 
has  remarked  in  relation  to  the  present  subject  in  his 
address  at  Belfast  (1874),  and  as  Sachs  repeatedly 
insists,*  the  embryos  of  some  plants  secrete  a fluid 
which  dissolves  albuminous  substances  out  of  the 
endosperm ; although  the  endosperm  is  not  actually 
united  with,  only  in  contact  with,  the  embryo.  All 
plants,  moreover,  have  the  power  of  dissolving  albu- 
minous or  proteid  substances,  such  as  protoplasm, 
chlorophyll,  gluten,  aleurone,  and  of  carrying  them 
from  one  part  to  other  parts  of  their  tissues.  This 
must  be  effected  by  a solvent,  probably  consisting  of 
a ferment  together  with  an  acid.f  Now,  in  the  case  of 
plants  which  are  able  to  absorb  already  soluble  matter 
from  captured  insects,  though  not  capable  of  true 
digestion,  the  solvent  just  referred  to,  which  must  be 
occasionally  present  in  the  glands,  would  be  apt  to 
exude  from  the  glands  together  with  the  viscid  secre- 
tion, inasmuch  as  endosmose  is  accompanied  by 
exosmose.  If  such  exudation  did  ever  occur,  the 
solvent  would  act  on  the  animal  matter  contained 
within  the  captured  insects,  and  this  would  be  an 
act  of  true  digestion.  As  it  cannot  be  doubted 
that  this  process  would  be  of  high  service  to  plants 


♦ ‘Traite  de  Botanique,’  3rd 
edit.  1874,  p.  844.  See  also  for 
following  facts  pp.  64,  76,  828, 
831. 

t Since  this  sentence  was  writ- 
ten, I have  reseived  a paper  by 
Gorup-Besanez  (‘Berichte  der 
Deutschen  Chem.  Gesellschaft,* 


Berlin,  1874,  p.  1478),  who,  with 
the  aid  of  Dr.  H.  Will,  has  ac- 
tually made  the  discovery  that  the 
seeds  of  the  vetch  contain  a fer- 
ment, which,  when  extracted  by 
glycerine,  dissolves  albuminous 
substances,  such  as  fibrin,  and 
converts  them  into  true  peptones. 


Chap.  XV. 


OK  THE  DEOSEEACE^. 


363 


growing  in  very  poor  soil,  it  would  tend  to  be  perfected 
through  natural  selection.  Therefore,  any  ordinary 
plant  having  viscid  glands,  which  occasionally  caught 
insects,  might  thus  be  converted  under  favourable  cir- 
cumstances into  a species  capable  of  true  digestion.  It 
ceases,  therefore,  to  be  any  great  mystery  how  several 
genera  of  plants,  in  no  way  closely  related  together, 
have  independently  acquired  this  same  power. 

As  there  exist  several  plants  the  glands  of  which 
cannot,  as  far  as  is  known,  digest  animal  matter,  yet 
can  absorb  salts  of  ammonia  and  animal  fluids,  it  is 
probable  that  this  latter  power  forms  the  first  stage 
towards  that  of  digestion.  It  might,  however,  happen, 
under  certain  conditions,  that  a plant,  after  having 
acquired  the  power  of  digestion,  should  degenerate 
into  one  capable  only  of  absorbing  animal  matter  in 
solution,  or  in  a state  of  decay,  or  the  final  products 
of  decay,  namely  the  salts  of  ammonia.  It  would  appear 
that  this  has  actually  occurred  to  a partial  extent  with 
the  leaves  of  Aldrovanda;  the  outer  parts  of  which 
possess  absorbent  organs,  but  no  glands  fitted  for  the 
secretion  of  any  digestive  fluid,  these  being  confined 
to  the  inner  parts. 

Little  light  can  be  thrown  on  the  gradual  acquire- 
ment of  the  third  remarkable  character  possessed  by 
the  more  highly  developed  genera  of  the  Droseracese, 
namely  the  power  of  movement  when  excited.  It 
should,  however,  be  borne  in  mind  that  leaves  and 
their  homologues,  as  well  as  flower-peduncles,  have 
gained  this  power,  in  innumerable  instances,  indepen- 
dently of  inheritance  from  any  common  parent  form ; 
for  instance,  in  tendril-bearers  and  leaf-climbers  (i.  e. 
plants  with  their  leaves,  petioles  and  flower-peduncles, 
&c.,  modified  for  prehension)  belonging  to  a large 


364 


CONCLUDING  REMARKS 


Chap.  XV* 


number  of  the  most  widely  distinct  orders, — in  the 
leaves  of  the  many  plants  which  go  to  sleep  at  night, 
or  move  when  shaken, — and  in  the  irritable  stamens 
and  pistils  of  not  a few  species.  We  may  therefore 
infer  that  the  power  of  movement  can  be  by  some 
means  readily  acquired.  Such  movements  imply  irri- 
tability or  sensitiveness,  but,  as  Cohn  has  remarked,* 
the  tissues  of  the  plants  thus  endowed  do  not  differ 
in  any  uniform  manner  from  those  of  ordinary  plants ; 
it  is  therefore  probable  that  all  leaves  are  to  a slight 
degree  irritable.  Even  if  an  insect  alights  on  a leaf, 
a slight  molecular  change  is  probably  transmitted 
to  some  distance  across  its  tissue,  with  the  sole 
difference  that  no  perceptible  effect  is  produced.  We 
have  some  evidence  in  favour  of  this  belief,  for  we 
know  that  a single  touch  on  the  glands  of  Drosera  does 
not  excite  inflection ; yet  it  must  produce  some  effect, 
for  if  the  glands  have  been  immersed  in  a solution  of 
camphor,  inflection  follows  within  a shorter  time  than 
would  have  followed  from  the  effects  of  camphor 
alone.  So  again  with  Dionsea,  the  blades  in  their 
ordinary  state  may  be  roughly  touched  without  their 
closing;  yet  some  effect  must  be  thus  caused  and 
transmitted  across  the  whole  leaf,  for  if  the  glands  have 
recently  absorbed  animal  matter,  even  a delicate  touch 
causes  them  to  close  instantly.  On  the  whole  we  may 
conclude  that  the  acquirement  of  a high  degree  of 
sensitiveness  and  of  the  power  of  movement  by  certain 
genera  of  the  Droseraceae  presents  no  greater  difliculty 
than  that  presented  by  tne  similar  but  feebler  powers 
of  a multitude  of  other  plants. 


* See  the  abstract  of  his  me-  Mag.  of  Nat.  Hist.’  3rd  series^ 
moir  on  the  contractile  tissues  vol.  xi.  p.  188. 
of  plants,  in  the  ‘ Annals  and 


Chap.  XV. 


ON  THE  DKOSERACE^. 


365 


The  specialised  nature  of  the  sensitiveness  possessed 
by  Drosera  and  Dionaea,  and  by  certain  other  plants, 
well  deserves  attention.  A gland  of  Drosera  may  be 
forcibly  hit  once,  twice,  or  even  thrice,  without  any 
effect  being  produced,  whilst  the  continued  pressure 
of  an  extremely  minute  particle  excites  movement. 
On  the  other  hand,  a particle  many  times  heavier 
may  be  gently  laid  on  one  of  the  filaments  of 
Dionaea  with  no  effect;  but  if  touched  only  once  by 
the  slow  movement  of  a delicate  hair,  the  lobes  close ; 
and  this  difference  in  the  nature  of  the  sensitiveness  of 
these  two  plants  stands  in  manifest  adaptation  to  their 
manner  of  capturing  insects.  So  does  the  fact,  that 
when  the  central  glands  of  Drosera  absorb  nitro- 
genous matter,  they  transmit  a motor  impulse  to  the 
exterior  tentacles  much  more  quickly  than  when  they 
are  mechanically  irritated;  whilst  with  Dionsea  the 
absorption  of  nitrogeneous  matter  causes  the  lobes 
to  press  together  with  extreme  slowness,  whilst  a 
touch  excites  rapid  movement.  Somewhat  analogous 
cases  may  be  observed,  as  I have  shown  in  another 
work,  with  the  tendrils  of  various  plants  ; some  being 
most  excited  by  contact  with  fine  fibres,  others  by 
contact  with  bristles,  others  with  a flat  or  a creviced 
surface.  The  sensitive  organs  of  Drosera  and  Dionsea 
are  also  specialised,  so  as  not  to  be  uselessly  affected 
by  the  weight  or  impact  of  drops  of  rain,  or  by 
blasts  of  air.  This  may  be  accounted  for  by  sup- 
posing that  these  plants  and  their  progenitors  have 
grown  accustomed  to  the  repeated  action  of  rain  and 
wind,  so  that  no  molecular  change  is  thus  induced; 
whilst  they  have  been  rendered  more  sensitive  by 
means  of  natural  selection  to  the  rarer  impact  or 
pressure  of  solid  bodies.  Although  the  absorption  by 
the  glands  of  Drosera  of  various  fluids  excites  move- 


366 


CONCLUDING  REMAEKS 


Chap.  XV 


ment,  there  is  a great  difference  in  the  action  of 
allied  fluids;  for  instance,  between  certain  vegetable 
acids,  and  between  citrate  and  phosphate  of  ammonia. 
The  specialised  nature  and  perfection  of  the  sensitive- 
ness in  these  two  plants  is  all  the  more  astonishing 
as  no  one  supposes  that  they  possess  nerves ; and  by 
testing  Drosera  with  several  substances  which  act 
powerfully  on  the  nervous  system  of  animals,  it  does 
not  appear  that  they  include  any  diffused  matter 
analogous  to  nerve-tissue. 

Although  the  cells  of  Drosera  and  Dionsea  are  quite 
as  sensitive  to  certain  stimulants  as  are  the  tissues 
which  surround  the  terminations  of  the  nerves  in 
the  higher  animals,  yet  these  plants  are  inferior  even 
to  animals  low  down  in  the  scale,  in  not  being  affected 
except  by  stimulants  in  contact  with  their  sensitive 
parts.  They  would,  however,  probably  be  affected  by 
radiant  heat ; for  warm  water  excites  energetic  move- 
ment. When  a gland  of  Drosera,  or  one  of  the  fila- 
ments of  Dionaea,  is  excited,  the  motor  impulse  radiates 
in  all  directions,  and  is  not,  as  in  the  case  of  animals, 
directed  towards  special  points  or  organs.  This  holds 
good  even  in  the  case  of  Drosera  when  some  exciting 
substance  has  been  placed  at  two  points  on  the  disc, 
and  when  the  tentacles  all  round  are  inflected  with 
marvellous  precision  towards  the  two  points.  The 
rate  at  which  the  motor  impulse  is  transmitted,  though 
rapid  in  Dionaea,  is  much  slower  than  in  most  or  all 
animals.  This  fact,  as  well  as  that  of  the  motor 
impulse  not  being  specially  directed  to  certain  points, 
are  both  no  doubt  due  to  the  absence  of  nerves.  Never- 
theless we  perhaps  see  the  prefigurement  of  the  forma- 
tion of  nerves  in  animals  in  the  transmission  of  the 
motor  impulse  being  so  much  more  rapid  down  the 
confined  space  within  the  tentacles  of  Drosera  than 


Chap.  XV.  ON  THE  DEOSEKACE^.  367 

elsewhere,  and  somewhat  more  rapid  in  a longitudinal 
than  in  a transverse  direction  across  the  disc.  These 
plants  exhibit  still  more  plainly  their  inferiority  to 
animals  in  the  absence  of  any  reflex  action,  except  in 
so  far  as  the  glands  of  Drosera,  when  excited  from  a 
distance,  send  back  some  influence  which  causes  the 
contents  of  the  cells  to  become  aggregated  down  to  the 
bases  of  the  tentacles.  But  the  greatest  inferiority  of 
all  is  the  absence  of  a central  organ,  able  to  receive 
impressions  from  all  points,  to  transmit  their  effects 
in  any  definite  direction,  to  s^.or<3  them  up  and  repro- 
duce them. 


368 


PINGUICULA  VULGARIS. 


Chap.  XVL 


CHAPTEE  XVI. 

PlXGUICILA. 

Pinguicula  vulgaris  — Structure  of  leaves  — Number  of  insects  and 
other  objects  caught  — Movement  of  the  margins  of  the  leaves  — 
Uses  of  this  movement  — Secretion,  digestion,  and  absorption  — 
Action  of  the  secretion  on  various  animal  and  vegetable  substances 
— The  effects  of  substances  not  containing  soluble  nitrogenous 
matter  on  the  glands  — Pinguicula  grandijiora  — Pinguicula  lusU 
tanica,  catches  insects — Movement  of  the  leaves,  secretion  and 
digestion. 

Pinguicula  vulgaris. — This  plant  grows  in  moist 
places,  generally  on  mountains.  It  bears  on  an  average 
eight,  rather  thick,  oblong,  light  green  leaves,  having 
scarcely  any  footstalk.  A full-sized  leaf  is  about 
inch  in  length  and  f inch  in  breadth.  The  young 
central  leaves  are  deeply  concave,  and  project  upwards ; 
the  older  ones  towards  the  outside  are  flat  or  convex, 
and  lie  close  to  the  ground,  forming  a rosette 
from  3 to  4 inches  in  diameter.  The  margins  of  the 
leaves  are  incurved.  Their  upper  surfaces  are  thickly 
covered  with  two  sets  of  glandular  hairs,  differing  in 
the  size  of  the  glands  and  in  the  length  of  their 
pedicels.  The  larger  glands  have  a circular  outline  as 
seen  from  above,  and  are  of  moderate  thickness ; they 
are  divided  by  radiating  partitions  into  sixteen  cells, 
containing  light-green,  homogeneous  fluid.  They  are 
supported  on  elongated,  unicellular  pedicels  (contain- 
ing a nucleus  with  a nucleolus)  which  rest  on  slight 
prominences.  The  small  glands  differ  only  in  being 
formed  of  about  half  the  number  of  cells,  containing 
much  paler  fluid,  and  supported  on  much  shorter  pedi- 
cels. Near  the  midrib,  towards  the  base  of  the  leaf,  the 


C?HAP.  XVI. 


CAPTUKED  INSECTS. 


369 


pedicels  are  multicellular,  are  longer  than  elsewhere, 
and  bear  smaller  glands.  All  the  glands  secrete  a 
colourless  fluid,  which  is  so  viscid  that  I have  seen  a 
fine  thread  drawn  out  to  a length  of  18  inches;  but 
the  fluid  in  this  case  was  secreted  by  a gland  which 
had  been  excited.  The  edge  of  the  leaf  is  translucent, 
and  does  not  bear  any  glands;  and  here  the  spiral 
vessels,  proceeding  from  the  midrib,  terminate  in  cells 
marked  by  a spiral  line,  somewhat  like  those  within 
the  glands  of  Drosera. 

The  roots  are  short.  Three  plants  were  dug  up  in 
North  Wales  on  June  20,  and  carefully  washed ; 
each  bore  five  or  six  unbranched  roots,  the  longest  of 
which  was  only  1*2  of  an  inch.  Two  rather  young 
plants  were  examined  on  September  28 ; these  had  a 
greater  number  of  roots,  namely  eight  and  eighteen, 
all  under  1 inch  in  length,  and  very  little  branched. 

I was  led  to  investigate  the  habits  of  this  plant  by 
being  told  by  Mr.  W.  Marshall  that  on  the  mountains 
of  Cumberland  many  insects  adhere  to  the  leaves. 


A friend  sent  me  on  June  23  thirty-nine  leaves  from  Nortli 
Wales,  which  were  selected  owing  to  objects  of  some  kind  ad- 
hering to  them.  Of  these  leaves,  thirty-two  had  caught  142 
insects,  or  on  an  average  4*4  per  leaf,  minute  fragments  of 
insects  not  being  included.  Besides  the  insects,  small  leaves 
belonging  to  four  different  kinds  of  plants,  those  of  Erica  tetralix 
being  much  the  commonest,  and  three  minute  seedling  plants, 
blown  by  the  wind,  adhered  to  nineteen  of  the  leaves.  One  had 
caught  as  many  as  ten  leaves  of  the  Erica.  Seeds  or  fruits, 
commonly  of  Carex  and  one  of  Juncus,  besides  bits  of  moss 
and  other  rubbish,  likewise  adhered  to  six  of  the  thirty-nine 
leaves.  The  same  friend,  on  June  27,  collected  nine  plants 
bearing  seventy-four  leaves,  and  all  of  these,  with  the  exception 
of  three  young  leaves,  had  caught  insects ; thirty  insects  were 
counted  on  one  leaf,  eighteen  on  a second,  and  sixteen  on  a third. 
Another  friend  examined  on  August  22  some  plants  in  Donegal, 
Ireland,  and  found  insects  on  70  out  of  157  leaves;  fifteen  of 


370 


PINGUICULA  VULGAEIS. 


Chap.  XVL 


these  leaves  were  sent  me,  each  having  caught  on  an  average  2*4 
insects.  To  nine  of  them,  leaves  (mostly  of  Erica  tetralix)  ad- 
hered ; but  they  had  been  specially  selected  on  this  latter  account. 
I may  add  that  early  in  August  my  son  found  leaves  of  this  same 
Erica  and  the  fruits  of  a Carex  on  the  leaves  of  a Pinguicula 
in  Switzerland,  probably  Pinguicula  alpina ; some  insects,  but  no 
great  number,  also  adhered  to  the  leaves  of  this  plant,  which 
had  much  better  developed  roots  than  those  of  Pinguicula  vul- 
garis, In  Cumberland,  Mr.  Marshall,  on  September  3,  carefully 
examined  for  me  ten  plants  bearing  eighty  leaves ; and  on  sixty- 
three  of  these  (i.e.  on  79  per  cent.)  he  found  insects,  143  in 
number ; so  that  each  leaf  had  on  an  average  2*27  insects.  A 
few  days  later  he  sent  me  some  plants  with  sixteen  seeds  or 
fruits  adhering  to  fourteen  leaves.  There  was  a seed  on  three 
leaves  on  the  same  plant.  The  sixteen  seeds  belonged  to  nine 
different  kinds,  which  could  not  be  recognised,  excepting  one 
of  Kanunculus,  and  several  belonging  to  three  or  four  distinct 
species  of  Carex.  It  appears  that  fewer  insects  are  caught  late 
in  the  year  than  earlier ; thus  in  Cumberland  from  twenty  to 
twenty-four  insects  were  observed  in  the  middle  of  July  on 
several  leaves,  whereas  in  the  beginning  of  September  the 
average  number  was  only  2*27.  Most  of  the  insects,  in  all  the 
foregoing  cases,  were  Diptera,  but  with  many  minute  Hyme- 
noptera,  including  some  ants,  a few  small  Coleoptera,  larvae, 
spiders,  and  even  small  moths. 

We  thus  see  that  numerous  insects  and  other  objects 
are  caught  by  the  viscid  leaves ; but  we  have  no  right 
to  infer  from  this  fact  that  the  habit  is  beneficial  to 
the  plant,  any  more  than  in  the  before  given  case  of 
the  Mirabilis,  or  of  the  horse-chestnut.  But  it  will  pre- 
sently be  seen  that  dead  insects  and  other  nitrogenous 
bodies  excite  the  glands  to  increased  secretion ; and 
that  the  secretion  then  becomes  acid  and  has  the 
power  of  digesting  animal  substances,  such  as  albumen, 
fibrin,  &c.  Moreover,  the  dissolved  nitrogenous  matter 
is  absorbed  by  the  glands,  as  shown  by  their  limpid 
contents  being  aggregated  into  slowly  moving  gra- 
nular masses  of  protoplasm.  The  same  results  follow 
when  insects  are  naturally  captured,  and  as  the  plant 
lives  in  poor  soil  and  has  small  roots,  there  can  be  no 


Chap.  XVI. 


MOVEMENTS  OF  THE  LEAVES. 


371 


doubt  that  it  profits  by  its  power  of  digesting  and 
absorbing  matter  from  the  prey  which  it  habitually  cap- 
tures in  such  large  numbers.  It  will,  however,  be  con- 
venient first  to  describe  the  movements  of  the  leaves. 

Movements  of  the  Leaves. — ^That  such  thick,  large  leaves 
as  those  of  Pinguieula  vulgaris  should  have  the  power 
of  curving  inwards  when  excited  has  never  even  been 
suspected.  It  is  necessary  to  select  for  experiment 
leaves  with  their  glands  secreting  freely,  and  which 
have  been  prevented  from  capturing  many  insects ; as 
old  leaves,  at  least  those  growing  in  a state  of  nature, 
have  their  margins  already  curled  so  much  inwards 
that  they  exhibit  little  power  of  movement,  or  move 
very  slowly.  I will  first  give  in  detail  the  more 
important  experiments  which  were  tried,  and  then 
make  some  concluding  remarks. 

Experiment  1. — A young  and  almost  upright  leaf  was  selected, 
with  its  two  lateral  edges  equally  and  very  slightly  incurved. 
A row  of  small  flies  was  placed  along  one 
margin.  When  looked  at  next  day,  after 
15  hrs.,  this  margin,  but  not  the  other,  was 
found  folded  inwards,  like  the  helix  of  the 
human  ear,  to  the  breadth  of  of  an 
inch,  so  as  to  lie  partly  over  the  row  of 
flies  (fig.  15).  The  glands  on  which  the 
flies  rested,  as  well  as  those  on  the  over- 
lapping margin  which  had  been  brought 
into  contact  with  the  flies,  were  all  secreting 
copiously. 

Experiment  2. — A row  of  flies  was  placed 
on  one  margin  of  a rather  old  leaf,  which 
lay  flat  on  the  ground;  and  in  this  case 
the  margin,  after  the  same  interval  as  be- 
fore, namely  15  hrs.,  had  only  just  begun 
to  curl  inwards;  but  so  much  secretion  vuigans.) 

had  been  poured  forth  that  the  spoon-  ma!^S^1nflelted^ove/^a 
shaped  tip  of  the  leaf  was  filled  with  it.  flies. 

Experiment  3. — Fragments  of  a large  fly  were  placed  close  to 
the  apex  of  a vigorous  leaf,  as  well  as  along  half  one  margin. 


Fig.  ]5. 


372 


PINGUICULA  VULGARIS. 


Chap.  XVL 


After  4 hrs.  20  m.  there  was  decided  incurvation,  which  in- 
creased a little  during  the  afternoon,  but  was  in  the  same  state 
on  the  following  morning.  Near  the  apex  both  margins  were 
inwardly  curved.  I have  never  seen  a case  of  the  apex  itself 
being  in  the  least  curved  towards  the  base  of  the  leaf.  After 
48  hrs.  (always  reckoning  from  the  time  when  the  flies  were 
placed  on  the  leaf)  the  margin  had  everywhere  begun  to  unfold. 

Experiment  4. — A.  large  fragment  of  a fly  was  placed  on  a leaf, 
in  a medial  line,  a little  beneath  the  apex.  Both  lateral  mar- 
gins were  perceptibly  incurved  in  3 hrs.,  and  after  4 hrs.  20  m. 
to  such  a degree  that  the  fragment  was  clasped  by  both  margins. 
After  24  hrs.  the  two  infolded  edges  near  the  apex  (for  the  lower 
part  of  the  leaf  was  not  at  all  affected)  were  measured  and 
found  to  be  *11  of  an  inch  (2795  mm.)  apart.  The  fly  was  now 
removed,  and  a stream  of  water  poured  over  the  leaf  so  as  to 
wash  the  surface ; and  after  24  hrs.  the  margins  were  *25  of  an 
inch  (6*349  mm.)  apart,  so  that  they  were  largely  unfolded.  After 
an  additional  24  hrs.  they  were  completely  unfolded.  Another 
fly  was  now  put  on  the  same  spot  to  see  whether  this  leaf,  on 
which  the  first  fly  had  been  left  24  hrs.,  would  move  again; 
after  10  hrs.  there  was  a trace  of  incurvation,  but  this  did  not 
increase  during  the  next  24  hrs.  A bit  of  meat  was  also  placed 
on  the  margin  of  a leaf,  which  four  days  previously  had  become 
strongly  incurved  over  a fragment  of  a fly  and  had  afterwards 
re-expanded ; but  the  meat  did  not  cause  even  a trace  of  incur- 
vation. On  the  contrary,  the  margin  became  somewhat  reflexed, 
as  if  injured,  and  so  remained  for  the  three  following  days,  as 
long  as  it  was  observed. 

Experiment  5. — A large  fragment  of  a fly  was  placed  halfway 
between  the  apex  and  base  of  a leaf  and  halfway  between  the 
midrib  and  one  margin.  A short  space  of  this  margin,  opposite 
the  fly,  showed  a trace  of  incurvation  after  3 hrs.,  and  this 
became  strongly  pronounced  in  7 hrs.  After  24  hrs.  the  infolded 
edge  was  only  *16  of  an  inch  (4*064  mm.)  from  the  midrib. 
The  margin  now  began  to  unfold,  though  the  fly  was  left  on  the 
leaf ; so  that  by  the  next  morning  (i.e.  48  hrs.  from  the  time 
when  the  fly  was  first  put  on)  the  infolded  edge  had  almost 
completely  recovered  its  original  position,  being  now  *3  of  an 
inch  (7*62  mm.),  instead  of  *16  of  an  inch,  from  the  midrib. 
A trace  of  flexure  was,  however,  still  visible. 

Experiment  6. — A young  and  concave  leaf  was  selected  with 
its  margins  slightly  and  naturally  incurved.  Two  rather  large, 
oblong,  rectangular  pieces  of  roast  meat  were  placed  with  their 
ends  touching  the  infolded  edge,  and  *46  of  an  inch  (11*68  mm.) 


Chai  . XVI. 


MOVEMENTS  OF  THE  LEAVES. 


373 


apart  from  one  another.  After  24  hrs.  the  margin  was  greatly 
and  equally  incurved  (see  fig.  16)  throughout  this  space,  and  for 
a length  of  -12  or  *13  of  an  inch  (3*048  or  3*302  mm.)  above  and 
below  each  bit;  so  that  the  margin  had  been  affected  over  a 
greater  length  between  the  two  bits,  owing  to  their  conjoint 
action,  than  beyond  them.  The  bits  of  meat  were  too  large  to 
be  clasped  by  the  margin,  but  they  were  tilted  up,  one  of  them  so 
as  to  stand  almost  vertically.  After  48  hrs. 
the  margin  was  almost  unfolded,  and  the 
bits  had  sunk  down.  When  again  exa- 
mined after  two  days,  the  margin  was  quite 
unfolded,  with  the  exception  of  the  natu- 
rally inflected  edge ; and  one  of  the  bits 
of  meat,  the  end  of  which  had  at  first 
touched  the  edge,  was  now  *067  of  an  inch 
(1*70  mm.)  distant  from  it;  so  that  this 
bit  had  been  pushed  thus  far  across  the 
blade  of  the  leaf. 

Experiment  7. — A bit  of  meat  was  placed 
close  to  the  incurved  edge  of  a rather  young 
leaf,  and  after  it  had  re-expanded,  the  bit 
was  left  lying  *11  of  an  inch  (2*795  mm.) 
from  the  edge.  The  distance  from  the  edge 
to  the  midrib  of  the  fully  expanded  leaf 
was  *35  of  an  inch  (8*89  mm.) ; so  that  the 
bit  had  been  pushed  inwards  and  across 
nearly  one-third  of  its  semi-diameter. 

Experiment  8. —Cubes  of  sponge,  soaked  in  a strong  infusion 
of  raw  meat,  were  placed  in  close  contact  with  the  incurved 
edges  of  two  leaves, — an  older  and  younger  one.  The  distance 
from  the  edges  to  the  midribs  was  carefully  measured.  After 

1 hr.  17  m.  there  appeared  to  be  a trace  of  incurvation.  After 

2 hrs.  17  m.  both  leaves  were  plainly  inflected;  the  distance 
between  the  edges  and  midribs  being  now  only  half  what  it  was 
at  first.  The  incurvation  increased  slightly  during  the  next 
4j  hrs.,  but  remained  nearly  the  s for  the  next  17  hrs.  30  m. 
In  35  hrs.  from  the  time  when  the  sponges  were  placed  on  the 
leaves,  the  margins  were  a little  unfolded — to  a greater  degree 
in  the  younger  than  in  the  older  leaf.  The  latter  was  not  quite 
unfolded  until  the  third  day,  and  now  both  bits  of  sponge  were 
left  at  the  distance  of  *1  of  an  inch  (2*54  mm.)  from  the  edges ; 
or  about  a quarter  of  the  distance  between  the  edge  and  midrib. 
A third  bit  of  sponge  adhered  to  the  edge,  and,  as  the  margin 
unfolded,  was  dragged  backwards,  into  its  original  position. 


Fig  16. 

{Pinguicula  vulgarig,) 

Outline  of  leaf,  with 
right  margin  inflected 
against  two  square  bits 
of  meat. 


374 


PINGUICULA  VULGARIS. 


CuAP.  XVL 


Experiment  9. — A chain  of  fibres  of  roast  meat,  as  thin  as 
bristles  and  moistened  with  saliva,  were  placed  down  one  whole 
side,  close  to  the  narrow,  naturally  incurved  edge  of  a leaf. 
In  3 hrs.  this  side  was  greatly  incurved  along  its  whole  length, 
and  after  8 hrs.  formed  a cylinder,  about  gV  (1*27 

mm.)  in  diameter,  quite  concealing  the  meat.  This  cylinder 
remained  closed  for  32  hrs.,  but  after  48  hrs.  was  half  unfolded, 
and  in  72  hrs.  was  as  open  as  the  opposite  margin  where  no 
meat  had  been  placed.  As  the  thin  fibres  of  meat  were  com- 
pletely overlapped  by  the  margin,  they  were  not  pushed  at  all 
inwards,  across  the  blade. 

Experiment  10. — Six  cabbage  seeds,  soaked  for  a night  in 
water,  were  placed  in  a row  close  to  the  narrow  incurved  edge  of 
a leaf.  We  shall  hereafter  see  that  these  seeds  yield  soluble 
matter  to  the  glands.  In  2 hrs.  25  m.  the  margin  was  decidedly 
inflected ; in  4 hrs.  it  extended  over  the  seeds  for  about  half 
their  breadth,  and  in  7 hrs.  over  three-fourths  of  their  breadth, 
forming  a cylinder  not  quite  closed  along  the  inner  side,  and 
about  *7  of  an  inch  (1*778  mm.)  in  diameter.  After  24  hrs. 
the  inflection  had  not  increased,  perhaps  had  decreased.  The 
glands  which  had  been  brought  into  contact  with  the  upper 
surfaces  of  the  seeds  were  now  secreting  freely.  In  36  hrs. 
from  the  time  when  the  seeds  were  put  on  the  leaf  the  margin 
had  greatly,  and  after  48  hrs.  had  completely,  re-expanded. 
As  the  seeds  were  no  longer  held  by  the  inflected  margin,  and 
as  the  secretion  was  beginning  to  fail,  they  rolled  some  way 
down  the  marginal  channel. 

Experiment  11.  — Fragments  of  glass  were  placed  on  the 
margins  of  two  fine  young  leaves.  After  2 hrs.  30  m.  the 
margin  of  one  certainly  became  slightly  incurved;  but  the 
inflection  never  increased,  and  disappeared  in  16  hrs.  30  m. 
from  the  time  when  the  fragments  were  first  applied.  With  the 
second  leaf  there  was  a trace  of  incurvation  in  2 hrs.  15  m., 
which  became  decided  in  4 hrs.  30  m.,  and  still  more  strongly 
pronounced  in  7 hrs.,  but  after  19  hrs.  30  ra.  had  plainly 
decreased.  The  fragments  excited  at  most  a slight  and  doubtful 
increase  of  the  secretion;  and  in  two  other  trials,  no  increase 
coiild  be  perceived.  Bits  of  coal-cinders,  placed  on  a leaf,  pro- 
duced no  effect,  either  owing  to  their  lightness  or  to  the  leaf 
being  torpid. 

Experiment  12. — We  will  now  turn  to  fluids.  A row  of  drops 
of  a strong  infusion  of  raw  meat  were  placed  along  the  margins 
of  two  leaves;  squares  of  sponge  soaked  in  the  same  infusion 
being  placed  on  the  opposite  margins.  My  object  was  to  ascer- 


CuAP.  XVL  MOVEMENTS  OF  THE  LEAVES. 


375 


tain  whether  a fluid  would  act  as  energetically  as  a substance 
yielding  the  same  soluble  matter  to  the  glands.  No  distinct 
difference  was  perceptible ; certainly  none  in  the  degree  of  in- 
curvation ; but  the  incurvation  round  the  bits  of  sponge  lasted 
rather  longer,  as  might  perhaps  have  been  expected  from  the 
sponge  remaining  damp  and  supplying  nitrogenous  matter  for  a 
longer  time.  The  margins,  with  the  drops,  became  plainly 
incurved  in  2 hrs.  17  m.  The  incurvation  subsequently  increased 
somewhat,  but  after  24  hrs.  had  greatly  decreased. 

Exj)eriment  13. — Drops  of  the  same  strong  infusion  of  raw 
meat  were  placed  along  the  midrib  of  a young  and  rather  deeply 
concave  leaf.  The  distance  across  the  broadest  part  of  the  leaf, 
between  the  naturally  incurved  edges,  was  *55  of  an  inch  (13*97 
mm.).  In  3 hrs.  27  m.  this  distance  was  a trace  less ; in  6 hrs. 
27  m.  it  was  exactly  '45  of  an  inch  (11'43  mm.),  and  had  therefore 
decreased  by  *1  of  an  inch  (2*54  mm.).  After  only  10  hrs.  37  m. 
the  margin  began  to  re-expand,  for  the  distance  from  edge  to 
edge  was  now  a trace  wider,  and  after  24  hrs.  20  m.  was  as 
great,  within  a hair's  breadth,  as  when  the  drops  were  first 
placed  on  the  leaf.  From  this  experiment  we  learn  that  the 
motor  impulse  can  be  transmitted  to  a distance  of  *22  of  an 
inch  (5*590  mm.)  in  a transverse  direction  from  the  midrib  to 
both  margins;  but  it  would  be  safer  to  say  *2  of  an  inch 
(5*08  mm.),  as  the  drops  spread  a little  beyond  the  midrib. 
The  incurvation  thus  caused  lasted  for  an  unusually  short  time. 

Experiment  14. — Three  drops  of  a solution  of  one  part  of 
carbonate  of  ammonia  to  218  of  water  (2  grs.  to  1 oz.)  were 
placed  on  the  margin  of  a leaf.  These  excited  so  much  secretion 
that  in  1 h.  22  m.  all  three  drops  ran  together ; but  although  the 
leaf  was  observed  for  24  hrs.,  there  was  no  trace  of  inflection. 
We  know  that  a rather  strong  solution  of  this  salt,  though  it 
does  not  injure  the  leaves  of  Drosera,  paralyses  their  power  of 
movement,  and  I have  no  doubt,  from  the  following  case,  that 
this  holds  good  with  Pinguicula. 

Experiment  15. — A row  of  drops  of  a solution  of  one  part  ol 
carbonate  of  ammonia  to  875  of  water  (1  gr.  to  2 oz.)  was  placed 
on  the  margin  of  a leaf.  In  1 hr.  there  was  apparently  some 
slight  incurvation,  and  this  was  well  marked  in  3 hrs.  30  m. 
After  24  hrs.  the  margin  was  almost  completely  re-expanded. 

Experiment  16. — A row  of  large  drops  of  a solution  of  one 
part  of  phosphate  of  ammonia  to  4375  of  water  (1  gr.  to  10  oz.) 
was  placed  along  the  margin  of  a leaf.  No  effect  was  produced, 
and  after  8 hrs.  fresh  drops  were  added  along  the  same  margin 
without  the  least  effect.  We  know  that  a solution  of  this 

17 


376 


PINGUICULA  VULGARIS. 


€hap.  XVL 


strength  acts  powerfully  on  Drosera,  and  it  is  just  possible  that 
the  solution  was  too  strong.  I regret  that  I did  not  try  a weaker 
solution. 

Experiment  17. — As  the  pressure  from  bits  of  glass  causes 
incurvation,  I scratched  the  margins  of  two  leaves  for  some 
minutes  with  a blunt  needle,  but  no  effect  was  produced.  The 
surface  of  a leaf  beneath  a drop  of  a strong  infusion  of  raw 
meat  was  also  rubbed  for  10.  m.  with  the  end  of  a bristle, 
so  as  to  imitate  the  struggles  of  a captured  insect;  but  this 
part  of  the  margin  did  not  bend  sooner  than  the  other  parts 
with  undisturbed  drops  of  the  infusion. 


We  learn  from  the  foregoing  experiments  that  the 
margins  of  the  leaves  curl  inwards  when  excited  by 
the  mere  pressure  of  objects  not  yielding  any  soluble 
matter,  by  objepts  yielding  such  matter,  and  by  some 
fluids — namely  ^ infusion  of  raw  meat  and  a weak 
solution  of  carbonate  of  ammonia.  A stronger  solu- 
tion of  two  grains  of  this  salt  to  an  ounce  of  water, 
though  exciting  copious  secretion,  paralyses  the  leaf. 
Drops  of  water  and  of  a solution  of  sugar  or  gum  did  not 
cause  any  movement.  Scratching  the  surface  of  the 
leaf  for  some  minutes  produced  no  effect.  Therefore, 
as  far  as  we  at  present  know,  only  two  causes — namely 
slight  continued  pressure  and  the  absorption  of  nitro- 
genous matter — excite  movement.  It  is  only  the 
margins  of  the  leaf  which  bend,  for  the  apex  never 
curves  towards  the  base.  The  pedicels  of  the  glan- 
dular hairs  have  no  power  of  movement.  I observed 
on  several  occasions  that  the  surface  of  the  leaf  be- 
came slightly  concave  where  bits  of  meat  or  large 
flies  had  long  lain,  but  this  may  have  been  due  to 
Injury  from  over-stimulation. 

The  shortest  time  in  which  plainly  marked  move- 
ment was  observed  was  2 hrs.  17  m.,  and  this  occurred 
when  eitlier  nitrogenous  substances  or  fluids  were 
placed  on  the  leaves ; but  I believe  that  in  some  cases 


Ghap.XVI.  movements  of  the  leaves.  377 

there  was  a trace  of  movement  in  1 hr.  or  1 hr.  30  m. 
The  pressure  from  fragments  of  glass  excites  move- 
ment almost  as  quickly  as  the  absorption  of  nitro- 
genous matter,  but  the  degree  of  incurvation  thus 
caused  is  much  less.  After  a leaf  has  become  well 
incurved  and  has  again  expanded,  it  will  not  soon 
answer  to  a fresh  stimulus.  The  margin  was  affected 
longitudinally,  upwards  or  downwards,  for  a distance  of 
T3  of  an  inch  (3*302  mm.)  from  an  excited  point,  but 
for  a distance  of  *46  of  an  inch  between  two  excited 
points,  and  transversely  for  a distance  of  *2  of  an 
inch  (5*08  mm.).  The  motor  impulse  is  not  accom- 
panied, as  in  the  case  of  Drosera,  by  any  influence 
causing  increased  secretion;  for  when  a single  gland 
was  strongly  stimulated  and  secreted  copiously,  the 
surrounding  glands  were  not  in  the  least  affected. 
The  incurvation  of  the  margin  is  independent  of  in- 
creased secretion,  for  fragments  of  glass  cause  little 
or  no  secretion,  and  yet  excite  movement;  whereas 
a strong  solution  of  carbonate  of  ammonia  quickly 
excites  copious  secretion,  but  no  movement. 

One  of  the  most  curious  facts  with  respect  to  the 
movement  of  the  leaves  is  the  short  time  during  which 
they  remain  incurved,  although  the  exciting  object  is 
left  on  them.  In  the  majority  of  cases  there  was  well- 
marked  re-expansion  within  24  hrs.  from  the  time 
when  even  large  pieces  of  meat,  &c.,  were  placed  on 
the  leaves,  and  in  all  cases  within  48  hrs.  In  one 
instance  the  margin  of  a leaf  remained  for  32  hrs. 
closely  inflected  round  thin  fibres  of  meat ; in  another 
instance,  when  a bit  of  sponge,  soaked  in  a strong  in- 
fusion of  raw  meat,  had  been  applied  to  a leaf,  the 
margin  began  to  unfold  in  35  hrs.  Fragments  of  glass 
keep  the  margin  incurved  for  a shorter  time  than  do 
nitrogenous  bodies ; for  in  the  former  case  there  was 


378 


PINGUICULA  VULCAEIS. 


Chap.  XVL 


complete  re-expansion  in  16  his.  30  m.  Nitrogenous 
fluids  act  for  a shorter  time  than  nitrogenous  sub- 
stances ; thus,  when  drops  of  an  infusion  of  raw  meat 
were  placed  on  the  midrib  of  a leaf,  the  incurved 
margins  began  to  unfold  in  only  10  hrs.  37  m.,  and 
this  was  the  quickest  act  of  re-expansion  observed  by 
me ; but  it  may  have  been  partly  due  to  the  distance 
of  the  margins  from  the  midrib  where  the  drops  lay. 

We  are  naturally  led  to  inquire  what  is  the  use  of 
this  movement  which  lasts  for  so  short  a time  ? If 
very  small  objects,  such  as  fibres  of  meat,  or  moderately 
small  objects,  such  as  little  flies  or  cabbage-seeds,  are 
placed  close  to  the  margin,  they  are  either  completely 
or  partially  embraced  by  it.  The  glands  of  the  over- 
lapping margin  are  thus  brought  into  contact  with 
such  objects  and  pour  forth  their  secretion,  afterwards 
absorbing  the  digested  matter.  But  as  the  incurvation 
lasts  for  so  short  a time,  any  such  benefit  can  be  of 
only  slight  importance,  yet  perhaps  greater  than  at 
first  appears.  The  plant  lives  in  humid  districts,  and 
the  insects  which  adhere  to  all  parts  of  the  leaf  are 
washed  by  every  heavy  shower  of  rain  into  the  narrow 
channel  formed  by  the  naturally  incurved  edges.  For 
instance,  my  friend  in  North  Wales  placed  several 
insects  on  some  leaves,  and  two  days  afterwards  (there 
having  been  heavy  rain  in  the  interval)  found  some  of 
them  quite  washed  away,  and  many  others  safely 
tucked  under  the  now  closely  inflected  margins,  the 
glands  of  which  all  round  the  insects  were  no  doubt 
secreting.  We  can  thus,  also,  understand  how  it  is 
that  so  many  insects,  and  fragments  of  insects,  are 
generally  found  lying  wi Ihin  the  incurved  margins 
of  the  leaves. 

The  incurvation  of  the  margin,  due  to  the  presence 
of  an  exciting  object,  must  be  serviceable  in  another 


Chap.  XVL  MOVEMENTS  OF  THE  LEAVES. 


379 


and  probably  more  important  way.  We  have  seen 
that  when  large  bits  of  meat,  or  of  sponge  soaked 
in  the  juice  of  meat,  were  placed  on  a leaf,  the  margin 
was  not  able  to  embrace  them,  but,  as  it  became 
incurved,  pushed  them  very  slowly  towards  the  middle 
of  the  leaf,  to  a distance  from  the  outside  of  fully 
•1  of  an  inch  (2*54  mm.),  that  is,  across  between 
one-third  and  one-fourth  of  the  space  between  the 
edge  and  midrib.  Any  object,  such  as  a moderately 
sized  insect,  would  thus  be  brought  slowly  into  contact 
with  a far  larger  number  of  glands,  inducing  much 
more  secretion  and  absorption,  than  would  otherwise 
have  been  the  case.  That  this  would  be  highly  ser- 
viceable to  the  plant,  we  may  infer  from  the  fact  that 
Drosera  has  acquired  highly  developed  powers  of  move- 
ment, merely  for  the  sake  of  bringing  all  its  glands 
into  contact  with  captured  insects.  So  again,  after 
a leaf  of  DionsBa  has  caught  an  insect,  the  slow 
pressing  together  of  the  two  lobes  serves  merely  to 
bring  the  glands  on  both  sides  into  contact  with  it, 
causing  also  the  secretion  charged  with  animal  matter 
to  spread  by  capillary  attraction  over  the  whole  sur- 
face. In  the  case  of  Pinguicula,  as  soon  as  an  insect 
has  been  pushed  for  some  little  distance  towards  the 
midrib,  immediate  re-expansion  would  be  beneficial,  as 
the  margins  could  not  capture  fresh  prey  until  they 
were  unfolded.  The  service  rendered  by  this  pushing 
action,  as  well  as  that  from  the  marginal  glands  being 
brought  into  contact  for  a short  time  with  the  upper 
surfaces  of  minute  captured  insects,  may  perhaps 
account  for  the  peculiar  movements  of  the  leaves; 
otherwise,  we  must  look  at  these  movements  as  a 
remnant  of  a more  highly  developed  power  formerly 
possessed  by  the  progenitors  of  the  genus. 

In  the  four  British  species,  and,  as  I hear  from 


380 


PINGUICULA  VULGARIS. 


Chap.  XTI. 


Prof.  Dyer,  in  most  or  all  the  species  of  the  genus, 
the  edges  of  the  leaves  are  in  some  degree  naturally 
and  permanently  incurved.  This  incurvation  serves, 
as  already  shown,  to  prevent  insects  from  being 
washed  away  by  the  rain ; but  it  likewise  serves  for 
another  end.  When  a number  of  glands  have  been 
powerfully  excited  by  bits  of  meat,  insects,  or  any  other 
stimulus,  the  secretion  often  trickles  down  the  leaf, 
and  is  caught  by  the  incurved  edges,  instead  of  rolling 
off  and  being  lost.  As  it  runs  down  the  channel,  fresh 
glands  are  able  to  absorb  the  animal  matter  held  in 
solution.  Moreover,  the  secretion  often  collects  in 
little  pools  within  the  channel,  or  in  the  spoon-like 
tips  of  the  leaves ; and  I ascertained  that  bits  of  albu- 
men, fibrin,  and  gluten,  are  here  dissolved  more 
quickly  and  completely  than  on  the  surface  of  the 
leaf,  where  the  secretion  cannot  accumulate;  and  so 
it  would  be  with  naturally  caught  insects.  The  secre- 
tion was  repeatedly  seen  thus  to  collect  on  the  leaves 
of  plants  protected  from  the  rain;  and  with  exposed 
plants  there  would  be  still  greater  need  of  some  pro- 
vision to  prevent,  as  far  as  possible,  the  secretion,  with 
its  dissolved  animal  matter,  being  wholly  lost. 

It  has  already  been  remarked  that  plants  growing 
in  a state  of  nature  have  the  margins  of  their  leaves 
much  more  strongly  incurved  than  those  grown  in 
pots  and  prevented  from  catching  many  insects.  We 
have  seen  that  insects  washed  down  by  the  rain  from 
all  parts  of  the  leaf  often  lodge  within  the  margins, 
which  are  thus  excited  to  curl  farther  inwards;  and 
we  may  suspect  that  this  action,  many  times  repeated 
during  the  life  of  the  plant,  leads  to  their  permanent 
and  well-marked  incurvation.  I regret  that  this  view 
did  not  occur  to  me  in  time  to  test  its  truth. 

It  may  here  be  added,  though  not  immediately 


Chap.  XVl.  SECRETION,  ABSORPTION,  DIGESTION.  381 

bearing  on  our  subject,  that  when  a plant  is  pulled 
up,  the  leaves  immediately  curl  downwards  so  as 
almost  to  conceal  the  roots, — a fact  which  has  been 
noticed  by  many  persons.  I suppose  that  this  is  due 
to  the  same  tendency  which  causes  the  outer  and  older 
leaves  to  lie  flat  on  the  ground.  It  further  appears 
that  the  flower-stalks  are  to  a certain  extent  irritable, 
for  Dr.  Johnson  states  that  they  ^^bend  backwards  if 
rudely  handled.”  * 

Secretion^  Absorption,  and  Digestion, — I will  first  give 
my  observations  and  experiments,  and  then  a summary 
of  the  results. 


The  Effects  of  Objects  containing  Soluble  Nitrogenous  Matter, 

(1)  Flies  were  placed  on  many  leaves,  and  excited  the  glands 
to  secrete  copiously ; the  secretion  always  becoming  acid,  though 
not  so  before.  After  a time  these  insects  were  rendered  so 
tender  that  their  limbs  and  bodies  could  be  separated  by  a 
mere  touch,  owing  no  doubt  to  the  digestion  and  disintegration 
of  their  muscles.  The  glands  in  contact  with  a small  fly  con- 
tinued to  secrete  for  four  days,  and  then  became  almost  dry. 
A narrow  strip  of  this  leaf  was  cut  off,  and  the  glands  of  the 
longer  and  shorter  hairs,  which  had  lain  in  contact  for  the 
four  days  with  the  fly,  and  those  which  had  not  touched  it, 
were  compared  under  the  microscope  and  presented  a won- 
derful contrast.  Those  which  had  been  in  contact  were  filled 
with  brownish  granular  matter,  the  others  with  homogeneous 
fluid.  There  could  therefore  be  no  doubt  that  the  former  had 
absorbed  matter  from  the  fly. 

(2)  Small  bits  of  roast  meaty  placed  on  a leaf,  always  caused 
much  acid  secretion  in  the  course  of  a few  hours — in  one  case 
within  40  m.  When  thin  fibres  of  meat  were  laid  along  the 
margin  of  a leaf  which  stood  almost  upright,  the  secretion  ran 
down  to  the  ground.  Angular  bits  of  meat,  placed  in  little 
pools  of  the  secretion  near  the  margin,  were  in  the  course  of 


* ‘ English  Botany,*  by  Sir  J.  E.  Smith ; with  coloured  figures  by 
J.  Sowerby ; edit,  of  1832,  tab.  24,  25,  26. 


382 


PINGUICULA  VULGARIS. 


Chap.  XVI. 


two  or  three  days  much  reduced  in  size,  rounded,  rendered 
more  or  less  colourless  and  transparent,  and  so  much  softened 
that  they  fell  to  pieces  on  the  slightest  touch.  In  only  one 
instance  was  a very  minute  particle  completely  dissolved,  and 
this  occurred  within  48  hrs.  When  only  a small  amount  of 
secretion  was  excited,  this  was  generally  absorbed  in  from  24  hrs. 
to  48  hrs. ; the  glands  being  left  dry.  But  when  the  supply  ot 
secretion  was  copious,  round  either  a single  rather  large  bit  of 
meat,  or  round  several  small  bits,  the  glands  did  not  become 
dry  until  six  or  seven  days  had  elapsed.  The  most  rapid  case 
of  absorption  observed  by  me  was  when  a small  drop  of  an 
infusion  of  raw  meat  was  placed  on  a leaf,  for  the  glands  here 
became  almost  dry  in  3 hrs.  20  m.  Glands  excited  by  small 
particles  of  meat,  and  which  have  quickly  absorbed  their  own 
secretion,  begin  to  secrete  again  in  the  course  of  seven  or  eight 
days  from  the  time  when  the  meat  was  given  them. 

(3)  Three  minute  cubes  of  tough  cartilage  from  the  leg- bone 
of  a sheep  were  laid  on  a leaf.  After  10  hrs.  30  m.  some  acid 
secretion  was  excited,  but  the  cartilage  appeared  little  or  not  at 
all  affected.  After  24  hrs.  the  cubes  were  rounded  and  much 
reduced  in  size ; after  32  hrs.  they  were  softened  to  the  centre, 
and  one  was  quite  liquefied ; after  35  hrs.  mere  traces  of  solid 
cartilage  were  left ; and  after  48  hrs.  a trace  could  still  be  seen 
through  a lens  in  only  one  of  the  three.  After  82  hrs.  not 
only  were  all  three,  cubes  completely  liquefied,  but  all  the  secre- 
tion was  absorbed  and  the  glands  left  dry. 

(4)  Small  cubes  of  albumen  were  placed  on  a leaf ; in  8 hrs. 
feebly  acid  secretion  extended  to  a distance  of  nearly  of  an 
inch  round  them,  and  the  angles  of  one  cube  were  rounded. 
After  24  hrs.  the  angles  of  all  the  cubes  were  rounded,  and 
they  were  rendered  throughout  very  tender ; after  30  hrs.  the 
secretion  began  to  decrease,  and  after  48  hrs.  the  glands  were 
left  dry;  but  very  minute  bits  of  albumen  were  still  left 
undissolved. 

(5)  Smaller  cubes  of  albumen  (about  or  of  an  inch, 
*508  or  *423  mm.)  were  placed  on  four  glands ; after  18  hrs.  one 
cube  was  completely  dissolved,  the  others  being  much  reduced 
in  size,  softened,  and  transparent.  After  24  hrs.  two  of  the 
cubes  were  completely  dissolved,  and  already  the  secretion  on 
these  glands  was  almost  wholly  absorbed.  After  42  hrs.  the 
two  other  cubes  were  completely  dissolved.  These  four  glands 
began  to  secrete  again  after  eight  or  nine  days. 

(6)  Two  large  cubes  ot  albumen  (fully  of  an  inch,  1*27  mm.) 
were  placed,  one  near  the  midrib  and  the  other  near  the  margin 


Chap.  XVI.  SECRETION,  ABSORPTION,  DIGESTION.  383 


of  a leaf ; in  6 hrs.  there  was  much  secretion,  which  after  48  hrs. 
accumulated  in  a little  pool  round  the  cube  near  the  margin. 
This  cube  was  much  more  dissolved  than  that  on  the  blade  of 
the  leaf ; so  that  after  three  days  it  was  greatly  reduced  in  size, 
with  all  the  angles  rounded,  but  it  was  too  large  to  be  wholly 
dissolved.  The  secretion  was  partially  absorbed  after  four  days. 
The  cube  on  the  blade  was  much  less  reduced,  and  the  glands 
on  which  it  rested  began  to  dry  after  only  two  days. 

(7)  Fibrin  excites  less  secretion  than  does  meat  or  albumen. 
Several  trials  were  made,  but  I will  give  only  three  of  them. 
Two  minute  shreds  were  placed  on  some  glands,  and  in  3 hrs. 
45  m.  their  secretion  was  plainly  increased.  The  smaller  shred 
of  the  two  was  completely  liquefied  in  6 hrs.  15  m.,  and  the  other 
in  24  hrs. ; but  even  after  48  hrs.  a few  granules  of  fibrin  could 
still  be  seen  through  a lens  floating  in  both  drops  of  secretion. 
After  56  hrs.  30  m.  these  granules  were  completely  dissolved. 
A third  shred  was  placed  in  a little  pool  of  secretion,  within 
the  margin  of  a leaf  where  a seed  had  been  lying,  and  this 
was  completely  dissolved  in  the  course  of  15  hrs.  30  m. 

(8)  Five  very  small  bits  of  gluten  were  placed  on  a leaf,  and 
they  excited  so  much  secretion  that  one  of  the  bits  glided 
down  into  the  marginal  furrow.  After  a day  all  flve  bits  seemed 
much  reduced  in  size,  but  none  were  wholly  dissolved.  On  the 
third  day  I pushed  two  of  them,  which  had  begun  to  dry,  on 
to  fresh  glands.  On  the  fourth  day  undissolved  traces  of  three 
out  of  the  five  bits  could  still  be  detected,  the  other  two  having 
quite  disappeared ; but  I am  doubtful  whether  they  had  really 
been  completely  dissolved.  Two  fresh  bits  were  now  placed, 
one  near  the  middle  and  the  other  near  the  margin  of  another 
leaf;  both  excited  an  extraordinary  amount  of  secretion;  that 
near  the  margin  had  a little  pool  formed  round  it,  and  was 
much  more  reduced  in  size  than  that  on  the  blade,  but  after 
four  days  was  not  completely  dissolved.  Gluten,  therefore, 
excites  the  glands  greatly,  but  is  dissolved  with  much  difficulty, 
exactly  as  in  the  case  of  Drosera.  I regret  that  I did  not  try 
this  substance  after  having  been  immersed  in  weak  hydrochloric 
acid,  as  it  would  then  probably  have  been  quickly  dissolved. 

(9)  A small  square  thin  piece  of  pure  gelatine,  moistened 
with  water,  was  placed  on  a leaf,  and  excited  very  little  secre- 
tion in  5 hrs.  30  m.,  but  later  in  the  day  a greater  amount. 
After  24  hrs.  the  whole  square  was  completely  liquefied;  and 
this  would  not  have  occurred  had  it  been  left  in  water.  The 
liquid  was  acid. 

(10)  Small  particles  of  chemically  prepared  casein  excited 


384 


PINGUICULA  VULGARIS. 


Chap.  XVL 


acid  secretion,  but  were  not  quite  dissolved  after  two  days ; and 
the  glands  then  began  to  dry.  Nor  could  their  complete  dis- 
solution have  been  expected  from  what  we  have  seen  with 
Drosera. 

(11)  Minute  drops  of  skimmed  were  placed  on  a leaf,  and 
these  caused  the  glands  to  secrete  freely.  After  3 hrs.  the  milk 
was  found  curdled,  and  after  23  hrs.  the  curds  were  dissolved. 
On  placing  the  now  clear  drops  under  the  microscope,  nothing 
could  be  detected  except  some  oil-globules.  The  secretion, 
therefore,  dissolves  fresh  casein. 

(12)  Two  fragments  of  a leaf  were  immersed  for  17  hrs., 
each  in  a drachm  of  a solution  of  carbonate  of  ammonia,  of  two 
strengths,  namely  of  one  part  to  437  and  218  of  water.  The 
glands  of  the  longer  and  shorter  hairs  were  then  examined,  and 
their  contents  found  aggregated  into  granular  matter  of  a 
brownish-green  colour.  These  granular  masses  were  seen  by 
iny  son  slowly  to  change  their  forms,  and  no  doubt  consisted  of 
protoplasm.  The  aggregation  was  more  strongly  pronounced, 
and  the  movements  of  the  protoplasm  more  rapid,  within  the 
glands  subjected  to  the  stronger  solution  than  in  the  others. 
The  experiment  was  repeated  with  the  same  result;  and  on 
this  occasion  I observed  that  the  protoplasm  had  shrunk  a little 
from  the  walls  of  the  single  elongated  cells  forming  the  pedicels. 
In  order  to  observe  the  process  of  aggregation,  a narrow  strip 
of  leaf  was  laid  edgeways  under  the  microscope,  and  the  glands 
were  seen  to  be  quite  transparent ; a little  of  the  stronger  solu- 
tion (viz.  one  part  to  218  of  water)  was  now  added  under  the 
covering  glass ; after  an  hour  or  two  the  glands  contained  very 
fine  granular  matter,  which  slowly  became  coarsely  granular 
and  slightly  opaque;  but  even  after  5 hrs.  not  as  yet  of  a 
brownish  tint.  By  this  time  a few  rather  large,  transparent, 
globular  masses  appeared  within  the  upper  ends  of  the  pedicels, 
and  the  protoplasm  lining  their  walls  had  shrunk  a little.  It 
is  thus  evident  that  the  glands  of  Pinguicula  absorb  carbonate 
of  ammonia ; but  they  do  not  absorb  it,  or  are  not  acted  on  by 
it,  nearly  so  quickly  as  those  of  Drosera. 

(13)  Little  masses  of  the  orange -coloured  pollen  of  the 
common  pea,  placed  on  several  leaves,  excited  the  glands  to 
secrete  freely.  Even  a very  few  grains  which  accidentally  fell 
on  a single  gland  caused  the  drop  surrounding  it  to  increase  so 
much  in  size,  in  23  hrs.,  as  to  be  manifestly  larger  than  the 
drops  on  the  adjoining  glands.  Grains  subjected  to  the  secretion 
for  48  hrs.  did  not  emit  their  tubes;  they  were  quite  dis- 
coloured, and  seemed  to  contain  less  matter  than  before ; that 


Chap.  XVL  SECRETION,  ABSORPTION,  DIGESTION.  385 


which  was  left  being  of  a dirty  colour,  including  globules  of  oil. 
They  thus  differed  in  appearance  from  other  grains  kept  in 
water  for  the  same  length  of  time.  The  glands  in  contact  with 
the  pollen-grains  had  evidently  absorbed  matter  from  them ; for 
they  had  lost  their  natural  pale-green  tint,  and  contained  aggre- 
gated globular  masses  of  protoplasm. 

(14)  Square  bits  of  the  leaves  of  spinach,  cabbage,  and  a 
saxifrage,  and  the  entire  leaves  of  Erica  tetralix,  all  excited  the 
glands  to  increased  secretion.  The  spinach  was  the  most  effec- 
tive, for  it  caused  the  secretion  evidently  to  increase  in  1 hr. 
40  m.,  and  ultimately  to  run  some  way  down  the  leaf ; but  the 
glands  soon  began  to  dry,  viz.  after  35  hrs.  The  leaves  of  Erica 
tetralix  began  to  act  in  7 hrs.  30  m.,  but  never  caused  much 
secretion ; nor  did  the  bits  of  leaf  of  the  saxifrage,  though  in 
this  case  the  glands  continued  to  secrete  for  seven  days.  Some 
leaves  of  Pinguicula  were  sent  me  from  North  Wales,  to  which 
leaves  of  Erica  tetralix  and  of  an  unknown  plant  adhered ; and 
the  glands  in  contact  with  them  had  their  contents  plainly 
aggregated,  as  if  they  had  been  in  contact  with  insects ; whilst 
the  other  glands  on  the  same  leaves  contained  only  clear 
homogeneous  fluid. 

(15)  Seeds, — A considerable  number  of  seeds  or  fruits  se- 
lected by  hazard,  some  fresh  and  some  a year  old,  some  soaked 
for  a short  time  in  water  and  some  not  soaked,  were  tried.  The 
ten  following  kinds,  namely  cabbage,  radish.  Anemone  nemo- 
rosa,  Rumex  acetosa,  Carex  sylvatica,  mustard,  turnip,  cress. 
Ranunculus  acris,  and  Avena  pubescens^  all  excited  much  secre- 
tion, which  was  in  several  cases  tested  and  found  always  acid. 
The  flve  first-named  seeds  excited  the  glands  more  than  the 
others.  The  secretion  was  seldom  copious  until  about  24  hrs. 
had  elapsed,  no  doubt  owing  to  the  coats  of  the  seeds  not  being 
easily  permeable.  Nevertheless,  cabbage  seeds  excited  some 
secretion  in  4 hrs.  30  m. ; and  this  increased  so  much  in  18  hrs. 
as  to  run  down  the  leaves.  The  seeds  or  properly  the  fruits  of 
Carex  are  much  oftener  found  adhering  to  leaves  in  a state  of 
nature  than  those  of  aoy  other  genus ; and  the  fruits  of  Carex 
sylvatica  excited  so  much  secretion  that  in  15  hrs.  it  ran  into 
the  incurved  edges;  but  the  glands  ceased  to  secrete  after 
40  hrs.  On  the  other  hand,  the  glands  on  which  the  seeds 
of  the  Rumex  and  Avena  rested  continued  to  secrete  for  nine 
days. 

The  nine  following  kinds  of  seeds  excited  only  a slight 
amount  of  secretion,  namely  celery,  parsnip,  caraway,  Linum 
grandiflorum,  Cassia,  Trifolium  pannonicum,  Plantago,  onion, 


386 


PINGUICULA  VULGARIS. 


Chap.  XYL 


and  Bromus.  Most  of  these  seeds  did  not  excite  any  secretion 
until  48  hrs.  had  elapsed,  and  in  the  case  of  the  Trifolimn  only 
one  seed  acted,  and  this  not  until  the  third  day.  Although  the 
seeds  of  the  Plantago  excited  very  little  secretion,  the  glands 
continued  to  secrete  for  six  days.  Lastly,  the  five  following 
kinds  excited  no  secretion,  though  left  on  the  leaves  for  two 
or  three  days,  namely  lettuce.  Erica  ietralix,  Atriplex  hortensis^ 
Phalaris  canariensis,  and  wheat.  Nevertheless,  when  the  seeds 
of  the  lettuce,  wheat,  and  Atriplex  were  split  open  and  applied 
to  leaves,  secretion  was  excited  in  considerable  quantity  in 
10  hrs.,  and  I believe  that  some  was  excited  in  six  hours.  In 
the  case  of  the  Atriplex  the  secretion  ran  down  to  the  margin, 
and  after  24  hrs.  I speak  of  it  in  my  notes  ‘^as  immense  in 
quantity  and  acid.’'  The  split  seeds  also  of  the  Trifolium  and 
celery  acted  powerfully  and  quickly,  though  the  whole  seeds 
caused,  as  we  have  seen,  very  little  secretion,  and  only  after  a 
long  interval  of  time.  A slice  of  the  common  pea,  which  how- 
ever was  not  tried  whole,  caused  secretion  in  2 hrs.  From 
these  facts  we  may  conclude  that  the  great  difference  in  the 
degree  and  rate  at  which  various  kinds  of  seeds  excite  secre- 
tion, is  chiefly  or  wholly  due  to  the  different  permeability 
of  their  coats. 

Some  thin  slices  of  the  common  pea,  which  had  been  pre- 
viously soaked  for  1 hr.  in  water,  were  placed  on  a leaf,  and 
quickly  excited  much  acid  secretion.  After  24  hrs.  these  slices 
were  compared  under  a high  power  with  others  left  in  water 
for  the  same  time ; the  latter  contained  so  many  fine  granules 
of  legumin  that  the  slide  was  rendered  muddy ; whereas  the 
slices  which  had  been  subjected  to  the  secretion  wore  much 
cleaner  and  more  transparent,  the  granules  of  legumin  appa- 
rently having  been  dissolved.  A cabbage  seed  which  had  lain 
for  two  days  on  a leaf  and  had  excited  much  acid  secretion, 
was  cut  into  slices,  and  these  were  compared  with  those  of 
a seed  which  had  been  left  for  the  same  time  in  water.  Those 
subjected  to  the  secretion  were  of  a paler  colour;  their  coats 
presenting  the  greatest  differences,  for  they  were  of  a pale  dirty 
tint  instead  of  chestnut-brown.  The  glands  on  which  the 
cabbage  seeds  had  rested,  as  well  as  those  bathed  by  the  sur- 
rounding secretion,  differed  greatly  in  appearance  from  the  other 
glands  on  the  same  leaf,  for  they  all  contained  brownish  granular 
matter,  proving  that  they  had  absorbed  matter  from  the  seeds. 

That  the  secretion  acts  on  the  seeds  was  also  shown  by  some 
of  them  being  killed,  or  by  the  seedlings  being  injured.  Fourteen 
cabbage  seeds  were  left  for  three  days  on  leaves  and  excited 


Chap.  XVI.  SECRETION,  ABSORPTION,  DIGESTION.  387 


niTicli  secretion;  they  were  then  placed  on  damp  sand  under 
conditions  known  to  be  favourable  for  germination.  Three 
never  germinated,  and  this  was  a far  larger  proportion  of  deaths 
than  occurred  with  seeds  of  the  same  lot,  which  had  not  been 
subjected  to  the  secretion,  but  were  otherwise  treated  in  the 
same  manner.  Of  the  eleven  seedlings  raised,  three  had  the 
edges  of  their  cotyledons  slightly  browned,  as  if  scorched ; and 
the  cotyledons  of  one  grew  into  a curious  indented  shape.  Two 
mustard  seeds  germinated;  but  their  cotyledons  were  marked 
with  brown  patches  and  their  radicles  deformed.  Of  two  radish 
seeds,  neither  germinated ; whereas  of  many  seeds  of  the  same 
lot  not  subjected  to  the  secretion,  all,  excepting  one,  germinated. 
Of  the  two  Rumex  seeds,  one  died  and  the  other  germinated ; 
but  its  radicle  was  brown  and  soon  withered.  Both  seeds  of  the 
Avena  germinated,  one  grew  well,  the  other  had  its  radicle  brown 
and  withered.  Of  six  seeds  of  the  Erica  none  germinated,  and 
when  cut  open  after  having  been  left  for  five  months  on  damp 
sand,  one  alone  seemed  alive.  Twenty-two  seeds  of  various 
kinds  were  found  adhering  to  the  leaves  of  plants  growing  in  a 
state  of  nature ; and  of  these,  though  kept  for  five  months  on 
damp  sand,  none  germinated,  some  being  then  evidently  dead. 


The  Effects  of  Objects  not  containing  Soluble  Nitrogenous  Matter, 

(16)  It  has  already  been  shown  that  bits  of  glass,  placed  on 
leaves,  excite  little  or  no  secretion.  The  small  amount  which 
lay  beneath  the  fragments  was  tested  and  found  not  acid.  A 
bit  of  wood  excited  no  secretion ; nor  did  the  several  kinds  of 
seeds  of  which  the  coats  are  not  permeable  to  the  secretion,  and 
which,  therefore,  acted  like  inorganic  bodies.  Cubes  of  fat,  left 
for  two  days  on  a leaf,  produced  no  effect. 

(17)  A particle  of  white  sugar,  placed  on  a leaf,  formed  in 
1 hr.  10  m.  a large  drop  of  fluid,  which  in  the  course  of  2 
additional  hours  ran  down  into  the  naturally  inflected  margin. 
This  fluid  was  not  in  the  least  acid,  and  began  to  dry  up,  or 
more  probably  was  absorbed,  in  5 hrs.  30  m.  The  experiment 
was  repeated ; particles  being  placed  on  a leaf,  and  others  of 
the  same  size  on  a slip  of  glass  in  a moistened  state ; both  being 
covered  by  a bell-glass.  This  was  done  to  see  whether  the 
increased  amount  of  fluid  on  the  leaves  could  be  due  to  mere 
deliquescence;  but  this  was  proved  not  to  be  the  case.  The 
particle  on  the  leaf  caused  so  much  secretion  that  in  the  course 
of  4 hrs.  it  ran  down  across  two-thirds  of  the  leaf.  After  8 hrs. 
the  leaf,  which  was  concave,  was  actually  filled  with  very  viscid 


388 


PINGUICULA  VULGARIS. 


Chap.  XVL 


fluid ; and  it  particularly  deserves  notice  that  this,  as  on  the 
former  occasion,  was  not  in  the  least  acid.  This  great  amount 
of  secretion  may  be  attributed  to  exosmose.  The  glands  which 
had  been  covered  for  24  hrs.  by  this  fluid  did  not  differ,  when 
examined  under  the  microscope,  from  others  on  the  same  leaf, 
which  had  not  come  into  contact  with  it.  This  is  an  interesting 
fact  in  contrast  with  the  invariably  aggregated  condition  of 
glands  which  have  been  bathed  by  the  secretion,  when  holding 
animal  matter  in  solution. 

(18)  Two  particles  of  gum  arahic  were  placed  on  a leaf,  and 
they  certainly  caused  in  1 hr.  20  m.  a slight  increase  of  secretion. 
This  continued  to  increase  for  the  next  5 hrs.,  that  is  for  as 
long  a time  as  the  leaf  was  observed. 

(19)  Six  small  particles  of  dry  starch  of  commerce  were  placed 
on  a leaf,  and  one  of  these  caused  some  secretion  in  1 hr.  15  m., 
and  the  others  in  from  8 hrs.  to  9 hrs.  The  glands  which  had  thus 
been  excited  to  secrete  soon  became  dry,  and  did  not  begin  to 
secrete  again  until  the  sixth  day.  A larger  bit  of  starch  was 
then  placed  on  a leaf,  and  no  secretion  was  excited  in  5 hrs. 
30  m. ; but  after  8 hrs.  there  was  a considerable  supply,  which 
increased  so  much  in  24  hrs.  as  to  run  down  the  leaf  to  the 
distance  of  f of  an  inch.  This  secretion,  though  so  abundant, 
was  not  in  the  least  acid.  As  it  was  so  copiously  excited, 
and  as  seeds  not  rarely  adhere  to  the  leaves  of  naturally 
growing  plants,  it  occurred  to  me  that  the  glands  might 
perhaps  have  the  power  of  secreting  a ferment,  like  ptyaline, 
capable  of  dissolving  starch ; so  I carefully  observed  the  above 
six  small  particles  during  several  days,  but  they  did  not  seem 
in  the  least  reduced  in  bulk.  A particle  was  also  left  for  two 
days  in  a little  pool  of  secretion,  wliich  had  run  down  from  a 
piece  of  spinach  leaf ; but  although  the  particle  was  so  minute 
no  diminution  was  perceptible.  We  may  therefore  conclude 
that  the  secretion  cannot  dissolve  starch.  The  increase  caused 
by  this  substance  may,  I presume,  be  attributed  to  exosmose. 
But  I am  surprised  that  starch  acted  so  quickly  and  powerfully 
as  it  did,  though  in  a less  degree  than  sugar.  * Colloids  are  known 
to  possess  some  slight  power  of  dialysis ; and  on  placing  the 
leaves  of  a Primula  in  water,  and  others  in  syrup  and  diffused 
starch,  those  in  the  starch  became  flaccid,  but  to  a less  degree 
and  at  a much  slower  rate  than  the  leaves  in  the  syrup ; those  in 
water  remaining  all  the  time  crisp. 


From  the  foregoing  experiments  and  observations  we 


Chap.  XVI.  SECRETION,  ABSORPTION,  DIGESTION.  389 

see  that  objects  not  containing  soluble  matter  have 
little  or  no  power  of  exciting  the  glands  to  secrete. 
Non-nitrogenous  fluids,  if  dense,  cause  the  glands  to 
pour  forth  a large  supply  of  viscid  fluid,  but  this  is 
not  in  the  least  acid.  On  the  other  hand,  the  secre- 
tion from  glands  excited  by  contact  with  nitrogenous 
solids  or  liquids  is  invariably  acid,  and  is  so  copious 
that  it  often  runs  down  the  leaves  and  collects 
within  the  naturally  incurved  margins.  The  secre- 
tion in  this  state  has  the  power  of  quickly  dissolving, 
that  is  of  digesting,  the  muscles  of  insects,  meat, 
cartilage,  albumen,  fibrin,  gelatine,  and  casein  as 
it  exists  in  the  curds  of  milk.  The  glands  are 
strongly  excited  by  chemically  prepared  casein  and 
gluten;  but  these  substances  (the  latter  not  having 
been  soaked  in  weak  hydrochloric  acid)  are  only 
partially  dissolved,  as  was  likewise  the  case  with 
Drosera.  The  secretion,  when  containing  animal 
matter  in  solution,  whether  derived  from  solids 
or  from  liquids,  such  as  an  infusion  of  raw  meat, 
milk,  or  a weak  solution  of  carbonate  of  ammonia, 
is  quickly  absorbed;  and  the  glands,  which  were 
before  limpid  and  of  a greenish  colour,  become  brownish 
and  contain  masses  of  aggregated  granular  matter. 
This  matter,  from  its  spontaneous  movements,  no  doubt 
consists  of  protoplasm.  No  such  effect  is  produced 
by  the  action  of  non-nitrogenous  fluids.  After  the 
glands  have  been  excited  to  secrete  freely,  they  cease 
for  a time  to  secrete,  but  begin  again  in  the  course  of 
a few  days. 

Glands  in  contact  with  pollen,  the  leaves  of  other 
plants,  and  various  kinds  of  seeds,  pour  forth  much 
acid  secretion,  and  afterwards  absorb  matter  probably 
of  an  albuminous  nature  from  them.  Nor  can  the 
benefit  thus  derived  be  insignificant,  for  a considerable 


390 


PINGUICULA  GRANDIFLORA. 


Chap.  XVI 


amount  of  pollen  must  be  blown  from  the  many 
wind-fertilised  carices,  grasses,  &c.,  growing  where 
Pinguicula  lives,  on  to  the  leaves  thickly  covered  with 
viscid  glands  and  forming  large  rosettes.  Even  a few 
grains  of  pollen  on  a single  gland  causes  it  to 
secrete  copiously.  We  have  also  seen  how  fre- 
quently the  small  leaves  of  Erica  tetralix  and  of 
other  plants,  as  well  as  various  kinds  of  seeds  and 
fruits,  especially  of  Carex,  adhere  to  the  leaves.  One 
leaf  of  the  Pinguicula  had  caught  ten  of  the  little 
leaves  of  the  Erica ; and  three  leaves  on  the  same 
plant  had  each  caught  a seed.  Seeds  subjected 
to  the  action  of  the  secretion  are  sometimes  killed, 
or  the  seedlings  injured.  We  may,  therefore,  con- 
clude that  Pinguicula  vulgaris,  with  its  small  roots, 
is  not  only  supported  to  a large  extent  by  the  extra- 
ordinary number  of  insects  which  it  habitually  cap- 
tures, but  likewise  draws  some  nourishment  from  the 
pollen,  leaves,  and  seeds  of  other  plants  which  often 
adhere  to  its  leaves.  It  is  therefore  partly  a vegetable 
as  well  as  an  animal  feeder. 

Pinguicula  grandiflora. 

This  species  is  so  closely  allied  to  the  last  that  it  is 
ranked  by  Dr.  Hooker  as  a sub-species.  It  differs 
chiefly  in  the  larger  size  of  its  leaves,  and  in  the 
glandular  hairs  near  the  basal  part  of  the  midrib 
being  longer.  But  it  likewise  differs  in  constitution ; 
I hear  from  Mr.  Ealfs,  who  was  so  kind  as  to  send 
me  plants  from  Cornwall,  that  it  grows  in  rather 
difierent  sites ; and  Dr.  Moore,  of  the  Glasnevin 
Botanic  Gardens,  informs  me  that  it  is  much  more 
manageable  under  culture,  growing  freely  and  flower- 
ing annually;  whilst  Pinguicula  vulgaris  has  to  be 
renewed  every  year.  Mr.  Ealfs  found  numerous 


Chap.  XVL 


PINGUICULA  LUSITANICA. 


391 


insects  and  fragments  of  insects  adhering  to  almost  all 
the  leaves.  These  consisted  chiefly  of  Diptera,  with 
some  Hymenoptera,  Homoptera,  Coleoptera,  and  a 
moth.  On  one  leaf  there  were  nine  dead  insects, 
besides  a few  still  alive.  He  also  observed  a few  fruits 
of  Carex  fulicaris,  as  well  as  the  seeds  of  this  same 
Pinguicula,  adhering  to  the  leaves.  I tried  only  two 
experiments  with  this  species;  firstly,  a fly  was  placed 
near  the  margin  of  a leaf,  and  after  16  hrs.  this  was 
found  well  inflected.  Secondly,  several  small  flies  were 
placed  in  a row  along  one  margin  of  another  leaf,  and 
by  the  next  morning  this  whole  margin  was  curled 
inwards,  exactly  as  in  the  case  of  Pinguicala  vulgaris. 

Pinguicula  lusitanica. 

This  species,  of  which  living  specimens  were  sent  me 
by  Mr.  Balfs  from  Cornwall,  is  very  distinct  from  the 
two  foregoing  ones.  The  leaves  are  rather  smaller, 
much  more  transparent,  and  are  marked  with  purple 
branching  veins.  The  margins  of  the  leaves  are  much 
more  involuted;  those  of  the  older  ones  extending 
over  a third  of  the  space  between  the  midrib  and  the 
outside.  As  in  the  two  other  species,  the  glandular 
hairs  consist  of  longer  and  shorter  ones,  and  have  the 
same  structure ; but  the  glands  difler  in  being  purple, 
and  in  often  containing  granular  matter  before  they 
have  been  excited.  In  the  lower  part  of  the  leaf,  almost 
half  the  space  on  each  side  between  the  midrib  and 
margin  is  destitute  of  glands  ; these  being  replaced  by 
long,  rather  stiff,  multicellular  hairs,  which  intercross 
over  the  midrib.  These  hairs  perhaps  serve  to  prevent 
insects  from  settling  on  this  part  of  the  leaf,  where 
there  are  no  viscid  glands  by  which  they  could  be 
caught ; but  it  is  hardly  probable  that  they  were 
developed  for  this  purpose.  The  spiral  vessels  pro- 


392 


PINGUICULA  LUSITANICA. 


Chap.  XVL 


ceeding  from  the  midrib  terminate  at  the  extreme 
margin  of  the  leaf  in  spiral  cells ; but  these  are  not  so 
well  developed  as  in  the  two  preceding  species.  The 
flower-peduncles,  sepals,  and  petals,  are  studded  with 
glandular  hairs,  like  those  on  the  leaves. 

The  leaves  catch  many  small  insects,  which  are 
found  chiefly  beneath  the  involuted  margins,  probably 
washed  there  by  the  rain.  The  colour  of  the  glands 
on  which  insects  have  long  lain  is  changed,  being 
either  brownish  or  pale  purple,  with  their  contents 
coarsely  granular ; so  that  they  evidently  absorb 
matter  from  their  prey.  Leaves  of  the  Erica  tetraUxy 
flowers  of  a Galium,  scales  of  grasses,  &c.  likewise 
adhered  to  some  of  the  leaves.  Several  of  the  ex- 
periments which  were  tried  on  Pinguicula  vulgaris  were 
repeated  on  Pinguicula  lusitanica,  and  these  will  now 
be  given. 

(1)  A moderately  sized  and  angular  bit  of  alhuraen  was 
placed  on  one  side  of  a leaf,  halfway  between  the  midrib  and 
the  naturally  involuted  margin.  In  2 hrs.  15  m.  the  glands 
poured  forth  much  secretion,  and  this  side  became  more 
infolded  than  the  opposite  one.  The  inflection  increased, 
and  in  3 hrs.  30  m.  extended  up  almost  to  the  apex.  After 
24  hrs.  the  margin  was  rolled  into  a cylinder,  the  outer  surface 
of  which  touched  the  blade  of  the  leaf  and  reached  to  within 
the  2V  of  an  inch  of  the  midrib.  After  48  hrs.  it  began  to 
unfold,  and  in  72  hrs.  was  completely  unfolded.  The  cube  was 
rounded  and  greatly  reduced  in  size;  the  remainder  being  in 
a semi-liquefied  state. 

(2)  A moderately  sized  bit  of  albumen  was  placed  near  the 
apex  of  a leaf,  under  the  naturally  incurved  margin.  In 
2 hrs.  30  m.  much  secretion  was  excited,  and  next  morning 
the  margin  on  this  side  was  more  incurved  than  the  opposite 
one,  but  not  to  so  great  a degree  as  in  the  last  case.  The  margin 
unfolded  at  the  same  rate  as  before.  A large  proportion  of  the 
albumen  was  dissolved,  a remnant  being  still  left. 

(3)  Large  bits  of  album, en  were  laid  in  a row  on  the  midribs 
of  two  leaves,  but  produced  in  the  course  of  24  hrs.  no  effect ; 


Ohap.  XVL 


PINGUICULA  LUSITANICA. 


393 


nor  could  this  have  been  expected,  for  even  had  glands 
existed  here,  the  long  bristles  would  have  prevented  the 
albumen  from  coming  in  contact  with  them.  On  both  leaves 
the  bits  were  now  pushed  close  to  one  margin,  and  in  3 hrs. 
30  m.  this  became  so  greatly  inflected  that  the  outer  surface 
touched  the  blade ; the  opposite  margin  not  being  in  the  least 
affected.  After  three  days  the  margins  of  both  leaves  with  the 
albumen  were  still  as  much  inflected  as  ever,  and  the  glands 
were  still  secreting  copiously.  With  Pinguicula  vulgaris  I have 
never  seen  inflection  lasting  so  long. 

(4)  Two  cabbage  seeds,  after  being  soaked  for  an  hour  in  water, 
were  placed  near  the  margin  of  a leaf,  and  caused  in  3 hrs. 
20  m.  increased  secretion  and  incurvation.  After  24  hrs.  the 
leaf  was  partially  unfolded,  but  the  glands  were  still  secreting 
freely.  These  began  to  dry  in  48  hrs.,  and  after  72  hrs.  were 
almost  dry.  The  two  seeds  were  then  placed  on  damp  sand 
under  favourable  conditions  for  growth;  but  they  never  ger- 
minated, and  after  a time  were  found  rotten.  They  had  no 
doubt  been  killed  by  the  secretion. 

(5)  Small  bits  of  a spinach  leaf  caused  in  1 hr.  20  m. 
increased  secretion ; and  after  3 hrs.  20  m.  plain  incurvation  of 
the  margin.  The  margin  was  well  inflected  after  9 hrs.  15  m., 
but  after  24  hrs.  was  almost  fully  re-expanded.  The  glands 
in  contact  with  the  spinach  became  dry  in  72  hrs.  Bits  of 
albumen  had  been  placed  the  day  before  on  the  opposite  margin 
of  this  same  leaf,  as  well  as  on  that  of  a leaf  with  cabbage 
seeds,  and  these  margins  remained  closely  inflected  for  72  hrs., 
showing  how  much  more  enduring  is  the  effect  of  albumen  than 
of  spinach  leaves  or  cabbage  seeds. 

(6)  A row  of  small  fragments  of  glass  was  laid  along  one 
margin  of  a leaf ; no  effect  was  produced  in  2 hrs.  10  m.,  but 
after  3 hrs.  25  m.  there  seemed  to  be  a trace  of  inflection,  and 
this  was  distinct,  though  not  strongly  marked,  after  6 hrs.  The 
glands  in  contact  with  the  fragments  now  secreted  more  freely 
than  before;  so  that  they  appear  to  be  more  easily  excited 
by  the  pressure  of  inorganic  objects  than  are  the  glands  of  Fin- 
guicula  vulgaris.  The  above  slight  inflection  of  the  margin  had 
not  increased  after  24  hrs.,  and  the  glands  were  now  beginning 
to  dry.  The  surface  of  a leaf,  near  the  midrib  and  towards 
the  base,  was  rubbed  and  scratched  for  some  time,  but  no 
movement  ensued.  The  long  hairs  which  are  situated  here 
were  treated  in  the  same  manner,  with  no  effect.  This  latter 
trial  was  made  because  I thought  that  the  hairs  might  perhaps 
be  sensitive  to  a touch,  like  the  filaments  of  Dionaea. 


394 


PINGUICULA  LUSITANICA. 


Chap.  XVL 


(7)  The  flower-peduncles,  sepals  and  petals,  bear  glands  in 
general  appearance  like  those  on  the  leaves.  A piece  of  a 
flower-peduncle  was  therefore  left  for  1 hr.  in  a solution  of 
one  part  of  carbonate  of  ammonia  to  437  of  water,  and  this 
caused  the  glands  to  change  from  bright  pink  to  a dull 
purple  colour ; but  their  contents  exhibited  no  distinct  aggre- 
gation. After  8 hrs.  30  m.  they  became  colourless.  Two  minute 
cubes  of  albumen  were  placed  on  the  glands  of  a flower- 
peduncle,  and  another  cube  on  the  glands  of  a sepal ; but  they 
were  not  excited  to  increased  secretion,  and  the  albumen 
after  two  days  was  not  in  the  least  softened.  Hence  these 
glands  apparently  differ  greatly  in  function  from  those  on  the 
leaves. 

From  the  foregoing  observations  on  Pinguicula  lusi- 
tanica  we  see  that  the  naturally  much  incurved  mar- 
gins of  the  leaves  are  excited  to  curve  still  farther  in- 
wards by  contact  with  organic  and  inorganic  bodies ; 
that  albumen,  cabbage  seeds,  bits  of  spinach  leaves, 
and  fragments  of  glass,  cause  the  glands  to  secrete 
more  freely ; — that  albumen  is  dissolved  by  the 
secretion,  and  cabbage  seeds  killed  by  it ; — and  lastly 
that  matter  is  absorbed  by  the  glands  from  the  insects 
which  are  caught  in  large  numbers  by  the  viscid 
secretion.  The  glands  on  the  flower-peduncles  seem 
to  have  no  such  power.  This  species  differs  from  Pin- 
guicala  vulgaris  and  grandijlora  in  the  margins  of  the 
leaves,  when  excited  by  organic  bodies,  being  inflected 
to  a greater  degree,  and  in  the  inflection  lasting  for  a 
longer  time.  The  glands,  also,  seem  to  be  more  easily 
excited  to  increased  secretion  by  bodies  not  yielding 
soluble  nitrogenous  matter.  In  other  respects,  as  far 
as  my  observations  serve,  all  three  species  agree  in 
their  functional  powers. 


Chap.  X\n. 


UTRICULARIA  NEGLECTA. 


395 


CHAPTER  XVIL 

Utriculaeia. 

Utricularia  neglecta — Structure  of  the  bladder — The  uses  of  the  several 
parts  — Number  of  imprisoned  animals  — Manner  of  capture  — 
The  bladders  cannot  digest  animal  matter,  but  absorb  the  products 
of  its  decay  — Experiments  on  the  absorption  of  certain  fluids  by 
the  quadrifid  processes  — Absorption  by  the  glands  — Summary 
of  the  observation  on  absorption  — Development  of  the  bladders  — 
Utricularia  vulgaris — Utricularia  minor — Utricularia  clandestina. 


I WAS  led  to  investigate  the  habits  and  structure  of 
the  species  of  this  genus  partly  from  their  belonging 
to  the  same  natural  family  as  Pinguicula,  but  more 
especially  by  Mr.  Holland’s  statement,  that  water 
insects  are  often  found  imprisoned  in  the  bladders,” 
which  he  suspects  are  destined  for  the  plant  to  feed 
on.”  * The  plants  which  I first  received  as  Utricularia 
vulgaris  from  the  New  Forest  in  Hampshire  and  from 
Cornwall,  and  which  I have  chiefly  worked  on,  have 
been  determined  by  Dr.  Hooker  to  be  a very  rare 
British  species,  the  Utricularia  neglecta  of  Lehm.f  I 
subsequently  received  the  true  Utricularia  vulgaris 
from  Yorkshire.  Since  drawing  up  the  following 
description  from  my  own  observations  and  those  of  my 
son,  Francis  Darwin,  an  important  memoir  by  Prof.  Cohn 


* The  Quart.  Mag.  of  the 
High  Wycombe  Nat.  Hist.  Soc.* 
July  1868,  p.  5.  Delpino  pUlt. 
Osservaz.  sulla  Dicogamia,*  &c. 
1868-1869,  p.  16)  also  quotes 
Crouan  as  having  found  (1858) 
crustaceans  'within  the  bladders 
of  Utricularia  vulgaris. 


t I am  much  indebted  to  the 
Rev.  H.  M.  Wilkinson,  of  Bistern, 
for  having  sent  me  several  fine 
lots  of  this  species  from  the  New 
Forest.  Mr.  Ralfs  was  also  so  kind 
as  to  send  me  living  plants  of  the 
same  species  from  near  Penzance 
in  Cornwall. 


396 


UTRICULARIA  NEGLECTA. 


Chap.  XVII. 


on  TJtricularia  vulgaris  has  appeared ; * and  it  has  been 
no  small  satisfaction  to  me  to  find  that  my  account 
agrees  almost  completely  with  that  of  this  distin- 
guished observer.  I will  publish  my  description  as 
it  stood  before  reading  that  by  Prof.  Cohn,  adding 
occasionally  some  statements  on  his  authority. 


Branch  with  the  divided  leaves  bearing  bladders;  about  twice  enlarged. 

TJtricularia  neglecta. — The  general  appearance  of  a 
branch  (about  twice  enlarged),  with  the  pinnatifid  leaves 
bearing  bladders,  is  represented  in  the  above  sketch 
(fig.  17).  The  leaves  continually  bifurcate,  so  that 
a full-grown  one  terminates  in  from  twenty  to  thirty 


* ‘ Beitrage  zur  Biologie  der  Pflanzen,  * drittes  Heft,  1875. 


Chap.  XVn.  STKUCTUKE  OF  THE  BLADDER.  397 

points.  Each  point  is  tipped  by  a short,  straight 
bristle  ; and  slight  notches  on  the  sides  of  the 
leaves  bear  similar  bristles.  On  both  surfaces  there 
are  many  small  papillae,  crowned  with  two  hemi- 
spherical cells  in  close  contact.  The  plants  float 
near  the  surface  of  the  water,  and  are  quite  destitute 
of  roots,  even  during  the  earliest  period  of  growth.* 
They  commonly  inhabit,  as  more  than  one  observer 
has  remarked  to  me,  remarkably  foul  ditches. 

The  bladders  offer  the  chief  point  of  interest. 
There  are  often  two  or  three  on  the  same  divided  leaf, 
generally  near  the  base ; though  I have  seen  a single 
one  growing  from  the  stem.  They  are  supported  on 
short  footstalks.  When  fully  grown,  they  are  nearly 
-fV  of  an  inch  (2*54  mm.)  in  length.  They  are  trans- 
lucent, of  a green  colour,  and  the  walls  are  formed 
of  two  layers  of  cells.  The  exterior  cells  are  poly- 
gonal and  rather  large ; but  at  many  of  the  points 
where  the  angles  meet,  there  are  smaller  rounded  cells. 
These  latter  support  short  conical  projections,  sur- 
mounted by  two  hemispherical  cells  in  such  close 
apposition  that  they  appear  united;  but  they  often 
separate  a little  when  immersed  in  certain  fluids.  The 
papillae  thus  formed  are  exactly  like  those  on  the 
surfaces  of  the  leaves.  Those  on  the  same  bladder 
vary  much  in  size ; and  there  are  a few,  especially  on 
very  young  bladders,  which  have  an  elliptical  instead 
of  a circular  outline.  The  two  terminal  cells  are 
transparent,  but  must  hold  much  matter  in  solution, 
judging  from  the  quantity  coagulated  by  prolonged 
immersion  in  alcohol  or  ether. 


* I infer  that  this  is  the  case  om  Lentibulariacese,”  from  the 
from  a drawing  of  a seedling  ‘ Videnskabelige  Meddelelser/ 
given  by  Dr.  Warming  in  his  Copenhagen,  1874,  Nos.  3-7,  pp. 
paper,  “Bidrag  til  Kundskaben  33-58. 


398 


UTRICULARIA  NEGLECTA. 


Chap.  XVII. 


The  bladders  are  filled  with  water.  They  generally, 
but  by  no  means  always,  contain  bubbles  of  air.  Ac- 
cording to  the  quantity  of  the  contained  water  and 
air,  they  vary  much  in  thickness,  but  are  always  some- 
what compressed.  At  an  early  stage  of  growth,  the 
flat  or  ventral  surface  faces  the  axis  or  stem;  but  the 
footstalks  must  have  some  power  of  movement ; for 
in  plants  kept  in  my  greenhouse  the  ventral  surface 
was  generally  turned  either  straight  or  obliquely 
downwards.  The  Eev.  H.  M.  Wilkinson  examined 


Bladder;  much  enlarged,  c,  collar  indistinctly  seen  through  the  walls. 

plants  for  me  in  a state  of  nature,  and  found  this 
commonly  to  be  the  case,  but  the  younger  bladders 
often  bad  their  valves  turned  upwards. 

The  general  appearance  of  a bladder  viewed  late- 
rally, with  the  appendages  on  the  near  side  alone 
represented,  is  shown  in  the  accompanying  figure 
(fig.  18).  The  lower  side,  where  the  footstalk  arises,  is 
nearly  straight,  and  I have  called  it  the  ventral  surface. 
The  other  or  dorsal  surface  is  convex,  and  terminates 
in  two  long  prolongations,  formed  of  several  rows  of 
cells,  conteming  chlorophyll,  and  bearing,  chiefly  on 


Chap.  XVn.  STRUCTUKE  OF  THE  BLADDER.  399 

the  outside,  six  or  seven  long,  pointed,  multicellular 
bristles.  These  prolongations  of  the  bladder  may  be 
conveniently  called  the  antennie,  for  the  whole  bladder 
(see  fig.  17)  curiously  resembles  an  entomostracan  crus- 
tacean, the  short  footstalk  representing  the  tail.  In 
fig.  18,  the  near  antenna  alone  is  shown.  Beneath 
the  two  antennao  the  end  of  the  bladder  is  slightly 
truncated,  and  here  is  situated  the  most  important 
part  of  the  whole  structure,  namely  the  entrance  and 
valve.  On  each  side  of  the  entrance  from  three  to 
rarely  seven  long,  multicellular  bristles  project  out- 


Valve  of  bladder;  greatly  enlarged. 

wards ; but  only  those  (four  in  number)  on  the  near 
side  are  shown  in  the  drawing.  These  bristles,  to- 
gether with  those  borne  by  the  antennae,  form  a sort 
of  hollow  cone  surrounding  the  entrance. 

The  valve  slopes  into  the  cavity  of  the  bladder,  or 
upwards  in  fig.  18.  It  is  attached  on  all  sides  to 
the  bladder,  excepting  by  its  posterior  margin,  or  the 
lower  one  in  fig.  19,  which  is  free,  and  forms  one  side 
of  the  slit-like  orifice  leading  into  the  bladder.  This 
margin  is  sharp,  thin,  and  smooth,  and  rests  on  the 
edge  of  a rim  or  collar,  which  dips  deeply  into  the 
18 


400 


XJTRICULARIA  NEGLECTA. 


Chap.  XVII 


bladder,  as  shown  in  the  longitudinal  section  (fig.  20) 
of  the  collar  and  valve ; it  is  also  shown  at  c,  in  fig.  18. 
The  edge  of  the  valve  can  thus  open  only  inwards. 
As  both  the  valve  and  collar  dip  into  the  bladder,  a 
hollow  or  depression  is  here  formed,  at  the  base  of 
which  lies  the  slit-like  orifice. 

The  valve  is  colourless,  highly  transparent,  flexible 
and  elastic.  It  is  convex  in  a transverse  direction, 
but  has  been  drawn  (fig.  19)  in  a flattened  state,  by 
which  its  apparent  breadth  is  increased.  It  is  formed, 


Fig.  20. 

* {Utricularia  neglecta.) 

Longitudinal  vertical  section  through  the  ventral  portion  of  a bladder;  showing  valve 
and  collar,  v,  valve ; the  whole  projection  above  c forms  the  collar ; b,  bifid  pro- 
cesses ; s,  ventral  surface  of  bladder. 

according  to  Cohn,  of  two  layers  of  small  cells,  which 
are  continuous  with  the  two  layers  of  larger  cells 
forming  the  walls  of  the  bladder,  of  which  it  is  evi- 
dently a prolongation.  Two  pairs  of  transparent 
pointed  bristles,  about  as  long  as  the  valve  itself, 
arise  from  near  the  free  posterior  margin  (fig.  18), 
and  point  obliquely  outwards  in  the  direction  of  the 
antennae.  There  are  also  on  the  surface  of  the  valve 
numerous  glands,  as  I will  call  them ; for  they  have 
the  power  of  absorption,  though  I doubt  whether 
they  ever  secrete.  They  consist  of  three  kinds,  which 


Chap.  XVIL  STRUCTURE  OF  THE  BLADDER. 


401 


to  a certain  extent  graduate  into  one  another.  Those 
situated  round  the  anterior  margin  of  the  valve  (upper 
margin  in  fig.  19)  are  very  numerous  and  crowded 
together ; they  consist  of  an  oblong  head  on  a long 
pedicel.  The  pedicel  itself  is  formed  of  an  elongated 
cell,  surmounted  by  a short  one.  The  glands  towards 
the  free  posterior  margin  are  much  larger,  few  in 
number,  and  almost  spherical,  having  short  footstalks ; 
the  head  is  formed  by  the  confluence  of  two  cells,  the 
lower  one  answering  to  the  short  upper  cell  of  the 
pedicel  of  the  oblong  glands.  The  glands  of  the 
third  kind  have  transversely  elongated  heads,  and  are 
seated  on  very  short  footstalks ; so  that  they  stand 
j)arallel  and  close  to  the  surface  of  the  valve ; they 
may  be  called  the  two-armed  glands.  The  cells  form- 
ing all  these  glands  contain  a nucleus,  and  are  lined 
by  a thin  layer  of  more  or  less  granular  protoplasm, 
the  primordial  utricle  of  Mohl.  They  are  filled  with 
fluid,  which  must  hold  much  matter  in  solution, 
judging  from  the  quantity  coagulated  after  they  have 
been  long  immersed  in  alcohol  or  ether.  The  depres- 
sion in  which  the  valve  lies  is  also  lined  with  innu- 
merable glands;  those  at  the  sides  having  oblong 
heads  and  elongated  pedicels,  exactly  like  the  glands 
on  the  adjoining  parts  of  the  valve. 

The  collar  (called  the  peristome  by  Cohn)  is  evi- 
dently formed,  like  the  valve,  by  an  inward  projection 
of  the  walls  of  the  bladder.  The  cells  composing  the 
outer  surface,  or  that  facing  the  valve,  have  rather 
thick  walls,  are  of  a brownish  colour,  minute,  very 
numerous,  and  elongated ; the  lower  ones  being  divided 
into  two  by  vertical  partitions.  The  whole  presents  a 
complex  and  elegant  appearance.  The  cells  forming 
the  inner  surface  are  continuous  with  those  over  the 
whole  inner  surface  of  the  bladder.  The  space  be- 


402 


UTEICULAEIA  NEGLECTA. 


Chap.  XVII 


tween  the  inner  and  outer  surface  consists  of  coarse 
cellular  tissue  (fig.  20).  The  inner  side  is  thickly 
covered  with  delicate  bifid  processes,  hereafter  to  be 
described.  The  collar  is  thus  made  thick ; and  it  is 
rigid,  so  that  it  retains  the  same  outline  whether  the 
bladder  contains  little  or  much  air  and  water.  This 
is  of  great  importance,  as  otherwise  the  thin  and 
flexible  valve  would  be  liable  to  be  distorted,  and 
in  this  case  would  not  act  properly. 

Altogether  the  entrance  into  the  bladder,  formed  by 
the  transparent  valve,  with  its  four  obliquely  project- 
ing bristles,  its  numerous  diversely  shaped  glands, 
surrounded  by  the  collar,  bearing  glands  on  the 
inside  and  bristles  on  the  outside,  together  with  the 
bristles  borne  by  the  antennae,  presents  an  extra- 
ordinarily complex  appearance  when  viewed  under 
the  microscope. 

We  will  now  consider  the  internal  structure  of  the 
bladder.  The  whole  inner  surface,  with  the  exception 
of  the  valve,  is  seen  under  a moderately  high  power  to 
be  covered  with  a serried  mass  of  processes  (fig.  21). 
Each  of  these  consists  of  four  divergent  arms  ; whence 
their  name  of  quadrifid  processes.  They  arise  from 
small  angular  cells,  at  the  junctions  of  the  angles  of 
the  larger  cells  which  form  the  interior  of  the 
bladder.  The  middle  part  of  the  upper  surface  of  these 
small  cells  projects  a little,  and  then  contracts  into  a 
very  short  and  narrow  footstalk  which  bears  the  four 
arms  (fig.  22).  Of  these,  two  are  long,  but  often  of  not 
quite  equal  length,  and  project  obliquely  inwards  and 
towards  the  posterior  end  of  the  bladder.  The  two 
others  are  much  shorter,  and  project  at  a smaller  angle, 
that  is,  are  more  nearly  horizontal,  and  are  directed 
towards  the  anterior  end  of  the  bladder.  These  arms 
are  only  moderately  sharp ; they  are  composed  of  ex* 


Chap.  XVII.  STRUCTURE  OF  THE  BLADDER.  403 

tremely  thin  transparent  membrane,  so  that  they  can 
be  bent  or  doubled  in  any  direction  without  being 
broken.  They  are  lined  with  a delicate  layer  of  proto- 
plasm, as  is  likewise  the  short  conical  projection  from 
which  they  arise.  Each  arm  generally  (but  not  in- 
variably) contains  a minute,  faintly  brown  particle, 
either  rounded  or  more  commonly  elongated,  which 
exhibits  incessant  Brownian  movements.  These  par- 


Fig.  21. 

Utricularia  neglecta.') 

Small  portion  of  inside  of  blad- 
der, much  enlarged,  showing  quad- 
rifid  processes. 


One  of  the  quadrifid  processes 
greatly  enlarged. 


tides  slowly  change  their  positions,  and  travel  from 
one  end  to  the  other  of  the  arms,  but  are  commonly 
found  near  their  bases.  They  are  present  in  the  quad- 
rifids  of  young  bladders,  when  only  about  a third  of 
their  full  size.  They  do  not  resemble  ordinary  nuclei, 
but  I believe  that  they  are  nuclei  in  a modified  con- 
dition, for  when  absent,  I could  occasionally  just  dis- 
tinguish in  their  places  a delicate  halo  of  matter, 
including  a darker  spot.  Moreover>  the  quadrifids  of 
Utricularia  montana  contain  rather  larger  and  much 


i04  UTEICULARIA  NEGLECTA.  Chap.  XVIL 

more  regularly  spherical,  but  otherwise  similar,  par- 
ticles, which  closely  resemble  the  nuclei  in  the  cells 
forming  the  walls  of  the  bladders.  In  the  present 
case  there  were  sometimes  two,  three,  or  even  more, 
nearly  similar  particles  within  a single  arm ; but,  as 
we  shall  hereafter  see,  the  presence  of  more  than 
one  seemed  always  to  be  connected  with  the  absorption 
of  decayed  matter. 

The  inner  side  of  the  collar  (see  the  previous  fig.  20) 
is  covered  with  several  crowded  rows  of  processes,  dif- 
fering in  no  important  respect  from  the  quadrifids, 
except  in  bearing  only  two  arms  instead  of  four ; they 
are,  however,  rather  narrower  and  more  delicate.  I shall 
call  them  the  bifids.  They  project  into  the  bladder, 
and  are  directed  towards  its  posterior  end.  The  quad- 
rifid  and  bifid  processes  no  doubt  are  homologous 
with  the  papillae  on  the  outside  of  the  bladder  and 
of  the  leaves;  and  we  shall  see  that  they  are  de- 
veloped from  closely  similar  papillae. 

The  Uses  of  the  several  Parts. — After  the  above  long 
but  necessary  description  of  the  parts,  we  will  turn  to 
their  uses.  The  bladders  have  been  supposed  by  some 
authors  to  serve  as  floats;  but  branches  which  bore 
no  bladders,  and  others  from  which  they  had  been 
removed,  floated  perfectly,  owing  to  the  air  in  the 
intercellular  spaces.  Bladders  containing  dead  and 
captured  animals  usually  include  bubbles  of  air,  but 
these  cannot  have  been  generated  solely  by  the  pro- 
cess of  decay,  as  I have  often  seen  air  in  young,  clean, 
and  empty  bladders ; and  some  old  bladders  with  much 
decaying  matter  had  no  bubbles. 

The  real  use  of  the  bladders  is  to  capture  small 
aquatic  animals,  and  this  they  do  on  a large  scale.  In 
the  first  lot  of  plants,  which  I received  from  the  New 
Forest  early  in  July,  a large  proportion  of  the  fully 


Chap.  XVn.  MANNER  OF  CAPTURING  PREY. 


405 


grown  bladders  contained  prey ; in  a second  lot,  re- 
ceived in  the  beginning  of  August,  most  of  the 
bladders  were  empty,  but  plants  had  been  selected 
which  had  grown  in  unusually  pure  water.  In  the 
first  lot,  my  son  examined  seventeen  bladders,  in- 
cluding prey  of  some  kind,  and  eight  of  these  con- 
tained entomostracan  crustaceans,  three  larvae  of  in- 
sects, one  being  still  alive,  and  six  remnants  of 
animals  so  much  decayed  that  their  nature  could  not 
be  distinguished.  I picked  out  five  bladders  which 
seemed  very  full,  and  found  in  them  four,  five,  eight, 
and  ten  crustaceans,  and  in  the  fifth  a single  much 
elongated  larva.  In  five  other  bladders,  selected  from 
containing  remains,  but  not  appearing  very  full,  there 
were  one,  two,  four,  two,  and  five  crustaceans.  A plant 
of  TJtricularia  vulgaris,  which  had  been  kept  in  almost 
pure  water,  was  placed  by  Cohn  one  evening  into  water 
swarming  with  crustaceans,  and  by  the  next  morning 
most  of  the  bladders  contained  these  animals  entrapped 
and  swimming  round  and  round  their  prisons.  They 
remained  alive  for  several  days ; but  at  last  perished, 
asphyxiated,  as  I suppose,  by  the  oxygen  in  the  water 
having  been  all  consumed.  Freshwater  worms  were 
also  found  by  Cohn  in  some  bladders.  In  all  cases 
the  bladders  with  decayed  remains  swarmed  with 
living  Alga©  of  many  kinds.  Infusoria,  and  other  low 
organisms,  which  evidently  lived  as  intruders. 

Animals  enter  the  bladders  by  bending  inwards  the 
posterior  free  edge  of  the  valve,  which  from  being 
highly  elastic  shuts  again  instantly.  As  the  edge  is 
extremely  thin,  and  fits  closely  against  the  edge  of  the 
collar,  both  projecting  into  the  bladder  (see  section, 
fig.  20),  it  would  evidently  be  very  difficult  for  any 
animal  to  get  out  when  once  imprisoned,  and  apparently 
they  never  do  escape.  To  show  how  closely  the  edge 


t06 


UTRICULARIA  NEGLECTA. 


Chap.  XVII 


fits,  I may  mention  that  my  son  found  a Daphnia 
which  had  inserted  one  of  its  antennae  into  the  slit, 
and  it  was  thus  held  fast  during  a whole  day.  On 
three  or  four  occasions  I haVe  seen  long  narrow  larvae, 
both  dead  and  alive,  wedged  between  the  corner  of 
the  valve  and  collar,  with  half  their  bodies  within  the 
bladder  and  half  out. 

As  I felt  much  difficulty  in  understanding  how  such 
minute  and  weak  animals,  as  are  often  captured, 
could  force  their  way  into  the  bladders,  I tried  many 
experiments  to  ascertain  how  this  was  effected.  The 
free  margin  of  the  valve  bends  so  easily  that  no 
resistance  is  felt  when  a needle  or  thin  bristle  is 
inserted.  A thin  human  hair,  fixed  to  a handle, 
and  cut  off  so  as  to  project  barely  ^ of  an  inch, 
entered  with  some  difficulty ; a longer  piece  yielded 
instead  of  entering.  On  three  occasions  minute  par- 
ticles of  blue  glass  (so  as  to  be  easily  distinguished) 
were  placed  on  valves  whilst  under  water;  and  on 
trying  gently  to  move  them  with  a needle,  they  disap- 
peared so  suddenly  that,  not  seeing  what  had  happened, 
I thought  that  I had  flirted  them  off;  but  on  ex- 
amining the  bladders,  they  were  found  safely  enclosed. 
The  same  thing  occurred  to  my  son,  who  placed  little 
cubes  of  green  box-wood  (about  of  an  inch,  *423 
mm.)  on  some  valves ; and  thrice  in  the  act  of  placing 
them  on,  or  whilst  gently  moving  them  to  another 
spot,  the  valve  suddenly  opened  and  they  were  en- 
gulfed. He  then  placed  similar  bits  of  wood  on  other 
valves,  and  moved  them  about  for  some  time,  but  they 
did  not  enter.  Again,  particles  of  blue  glass  were 
placed  by  me  on  three  valves,  and  extremely  minute 
shavings  of  lead  on  two  other  valves  ; after  1 or  2 hrs. 
none  had  entered,  but  in  from  2 to  5 hrs.  all  five 
were  enclosed.  One  of  the  particles  of  glass  was  a 


Chap.  XVIL  MANNER  OF  CAPTURING  PREY. 


407 


long  splinter,  of  which  one  end  rested  obliquely  on 
the  valve,  and  after  a few  hours  it  was  found  fixed,  half 
within  the  bladder  and  half  projecting  out,  with  the 
edge  of  the  valve  fitting  closely  all  round,  except  at 
one  angle,  where  a small  open  space  was  left.  It  was 
so  firmly  fixed,  like  the  above  mentioned  larvae,  that 
the  bladder  was  torn  from  the  branch  and  shaken,  and 
yet  the  splinter  did  not  fall  out.  My  son  also  placed 
little  cubes  (about  of  an  inch,  '391  mm.)  of  green 
box- wood,  which  were  just  heavy  enough  to  sink  in 
water,  on  three  valves.  These  were  examined  after 
19  hrs.  30  m.,  and  were  still  lying  on  the  valves  ; but 
after  22  hrs.  30  m.  one  was  found  enclosed.  I may 
here  mention  that  I found  in  a bladder  on  a naturally 
growing  plant  a grain  of  sand,  and  in  another  bladder 
three  grains ; these  must  have  fallen  by  some  accident 
on  the  valves,  and  then  entered  like  the  particles 
of  glass. 

The  slow  bending  of  the  valve  from  the  weight  of 
particles  of  glass  and  even  of  box-wood,  though  largely 
supported  by  the  water,  is,  I suppose,  analogous  to  the 
slow  bending  of  colloid  substances.  For  instance, 
particles  of  glass  were  placed  on  various  points  of 
narrow  strips  of  moistened  gelatine,  and  these  yielded 
and  became  bent  with  extreme  slowness.  It  is  much 
more  difficult  to  understand  how  gently  moving  a 
particle  from  one  part  of  a valve  to  another  causes  it 
suddenly  to  open.  To  ascertain  whether  the  valves 
were  endowed  with  irritability,  the  surfaces  of  several 
were  scratched  with  a needle  or  brushed  with  a fine 
camel-hair  brush,  so  as  to  imitate  the  crawling  move- 
ment of  small  crustaceans,  but  the  valve  did  not 
open.  Some  bladders,  before  being  brushed,  were  left 
for  a time  in  water  at  temperatures  between  80*^  and 
130°  F.  (26°*6 — 54°*4  Cent.),  as,  judging  from  a wide- 


408 


UTEICULARIA  NEGLECTA. 


Chap.  XVIL 


spread  analogy,  this  would  have  rendered  them  more 
sensitive  to  irritation,  or  would  by  itself  have  excited 
movement;  but  no  effect  was  produced.  We  may, 
therefore,  conclude  that  animals  enter  merely  by 
forcing  their  way  through  the  slit-like  orifice ; their 
heads  serving  as  a wedge.  But  I am  surprised  that 
such  small  and  weak  creatures  as  are  often  captured 
(for  instance,  the  nauplius  of  a crustacean,  and  a tardi- 
grade) should  be  strong  enough  to  act  in  this  manner, 
seeing  that  it  was  difficult  to  push  in  one  end  of  a 
bit  of  a hair  ^ of  an  inch  in  length.  Nevertheless, 
it  is  certain  that  weak  and  small  creatures  do  enter, 
and  Mrs.  Treat,  of  New  Jersey,  has  been  more  suc- 
cessful than  any  other  observer,  and  has  often  wit- 
nessed in  the  case  of  TJtricularia  clandestina  the 
whole  process.*  She  saw  a tardigrade  slowly  walk- 
ing round  a bladder,  as  if  reconnoitring ; at  last  it 
crawled  into  the  depression  where  the  valve  lies,  and 
then  easily  entered.  She  also  witnessed  the  entrap- 
ment of  various  minute  crustaceans.  Cypris  “was 
“ quite  wary,  but  nevertheless  was  often  caught. 
“ Coming  to  the  entrance  of  a bladder^  it  would  some- 
“ times  pause  a moment,  and  then  dash  away ; at 
“ other  times  it  would  come  close  up,  and  even  ven- 
“ ture  part  of  the  way  into  the  entrance  and  back  out 
“ as  if  afraid.  Another,  more  heedless,  would  open 
“ the  door  and  walk  in ; but  it  was  no  sooner  in  than 
“ it  manifested  alarm,  drew  in  its  feet  and  antennae, 
and  closed  its  shell.”  Larvae,  apparently  of  gnats, 
when  “feeding  near  the  entrance,  are  pretty  certain 
“ to  run  their  heads  into  the  net,  whence  there  is  no 
“ retreat.  A large  larva  is  sometimes  three  or  four 
“ hours  in  being  swallowed,  the  process  bringing  to 


* New  York  Tribune,  reprinted  in  the  ‘ Gard.  Chron.’  1875,  p.  303. 


Chap.  XVII.  MANNEB  OF  CAPTURING  PREY. 


409 


mind  what  I have  witnessed  when  a small  snake 
makes  a large  frog  its  victim.”  But  as  the  valve 
does  not  appear  to  be  in  the  least  irritable,  the 
slow  swallowing  process  must  be  the  effect  of  the 
onward  movement  of  the  larva. 

It  is  difficult  to  conjecture  what  can  attract  so  many 
creatures,  animal-  and  vegetable-feeding  crustaceans, 
worms,  tardigrades,  and  various  larvae,  to  enter  the 
bladders.  Mrs.  Treat  says  that  the  larvae  just 
referred  to  are  vegetable-feeders,  and  seem  to  have  a 
special  liking  for  the  long  bristles  round  the  valve,  but 
this  taste  will  not  account  for  the  entrance  of  animal- 
feeding crustaceans.  Perhaps  small  aquatic  animals 
habitually  try  to  enter  every  small  crevice,  like  that 
between  the  valve  and  collar,  in  search  of  food  or  pro- 
tection. It  is  not  probable  that  the  remarkable  trans- 
parency of  the  valve  is  an  accidental  circumstance, 
and  the  spot  of  light  thus  formed  may  serve  as  a 
guide.  The  long  bristles  round  the  entrance  ap- 
parently serve  for  the  same  purpose.  I believe  that 
this  is  the  case,  because  the  bladders  of  some  epi- 
phytic and  marsh  species  of  Utricularia  which  live 
embedded  either  in  entangled  vegetation  or  in  mud, 
have  no  bristles  round  the  entrance,  and  these  under 
such  conditions  would  be  of  no  service  as  a guide. 
Nevertheless,  with  these  epiphytic  and  marsh  species, 
two  pairs  of  bristles  project  from  the  surface  of  the 
valve,  as  in  the  aquatic  species ; and  their  use  pro- 
bably is  to  prevent  too  large  animals  from  trying  to 
force  an  entrance  into  the  bladder,  thus  rupturing  the 
orifice. 

As  under  favourable  circumstances  most  of  the  blad- 
ders succeed  in  securing  prey,  in  one  case  as  many  as 
ten  crustaceans  ; — as  the  valve  is  so  well  fitted  to 


ilO  UTEICULARIA  NEGLECTA.  Chap.  XVII 

allow  animals  to  enter  and  to  prevent  their  escape ; — 
and  as  the  inside  of  the  bladder  presents  so  singular 
a structure,  clothed  with  innumerable  quadrifid  and 
bifid  processes,  it  is  impossible  to  doubt  that  the  plant 
has  been  specially  adapted  for  securing  prey.  From 
the  analogy  of  Pinguicula,  belonging  to  the  same 
family,  I naturally  expected  that  the  bladders  would 
have  digested  their  prey  ; but  this  is  not  the  case,  and 
there  are  no  glands  fitted  for  secreting  the  proper 
fluid.  Nevertheless,  in  order  to  test  their  power  of 
digestion,  minute  fragments  of  roast  meat,  three  small 
cubes  of  albumen,  and  three  of  cartilage,  were  pushed 
through  the  orifice  into  the  bladders  of  vigorous 
plants.  They  were  left  from  one  day  to  three  days 
and  a half  within,  and  the  bladders  were  then  cut 
open ; but  none  of  the  above  substances  exhibited  the 
least  signs  of  digestion  or  dissolution ; the  angles  of  the 
cubes  being  as  sharp  as  ever.  These  observations  were 
made  subsequently  to  those  on  Drosera,  Dionjea,  Droso- 
phyllum,  and  Pinguicula ; so  that  I was  familiar  with 
the  appearance  of  these  substances  when  unde]> 
going  the  early  and  final  stages  of  digestion.  We  may 
therefore  conclude  that  Utricularia  cannot  digest  the 
animals  which  it  habitually  captures. 

In  most  of  the  bladders  the  captured  animals  are  so 
much  decayed  that  they  form  a pale  brown,  pulpy 
mass,  with  their  chitinous  coats  so  tender  that  they 
fall  to  pieces  with  the  greatest  ease.  The  black 
pigment  of  the  eye-spots  is  preserved  better  than  any 
thing  else.  Limbs,  jaws,  &c.  are  often  found  quite 
detached ; and  this  I suppose  is  the  result  of  the  vain 
struggles  of  the  later  captured  animals.  I have 
sometimes  felt  surprised  at  the  small  proportion  of 
imprisoned  animals  in  a fresh  state  compared  with 
those  utterly  decayed.  Mrs.  Treat  states  with  respect 


Ohap.  XVn.  ABSOEPTION  BY  THE  QUADRIFIDS. 


411 


to  the  larv8B  above  referred  to,  that  usually  in  less 
than  two  days  after  a large  one  was  captured  the  fluid 
contents  of  the  bladders  began  to  assume  a cloudy 
or  muddy  appearance,  and  often  became  so  dense 
that  the  outline  of  the  animal  was  lost  to  view.’* 
This  statement  raises  the  suspicion  that  the  bladders 
secrete  some  ferment  hastening  the  process  of  decay. 
There  is  no  inherent  improbability  in  this  supposition, 
considering  that  meat  soaked  for  ten  minutes  in  water 
mingled  with  the  milky  juice  of  the  papaw  becomes 
quite  tender  and  soon  passes,  as  Browne  remarks  in 
his  ^Natural  History  of  Jamaica,’  into  a state  of 
putridity. 

Whether  or  not  the  decay  of  the  imprisoned  animals 
is  in  any  way  hastened,  it  is  certain  that  matter  is 
absorbed  from  them  by  the  quadrifid  and  bifid  pro- 
cesses. The  extremely  delicate  nature  of  the  mem- 
brane of  which  these  processes  are  formed,  and  the 
large  surface  which  they  expose,  owing  to  their  number 
crowded  over  the  whole  interior  of  the  bladder,  are 
circumstances  all  favouring  the  process  of  absorption. 
Many  perfectly  clean  bladders  which  had  never  caught 
any  prey  were  opened,  and  nothing  could  be  distin- 
guished with  a No.  8 object-glass  of  Hartnack  within 
the  delicate,  structureless  protoplasmic  lining  of  the 
arms,  excepting  in  each  a single  yellowish  particle  or 
modified  nucleus.  Sometimes  two  or  even  three  such 
particles  were  present ; but  in  this  case  traces  of  decay- 
ing matter  could  generally  be  detected.  On  the  other 
hand,  in  bladders  containing  either  one  large  or  several 
small  decayed  animals,  the  processes  presented  a widely 
different  appearance.  Six  such  bladders  were  care- 
fully examined;  one  contained  an  elongated,  coiled- 
up  larva  ; another  a single  large  entomostracan  crusta- 
cean, and  the  others  from  two  to  five  smaller  ones,  all 


412  UTKICULARIA  NEGLECTA,  Chap.  XVIL 

in  a decayed  state.  In  these  six  bladders,  a largo 
number  of  the  quadrifid  processes  contained  transpa- 
rent, often  yellowish,  more  or  less  confluent,  spherical 
or  irregularly  shaped,  masses  of  matter.  Some  of  the 
processes,  however,  contained  only  fine  granular 
matter,  the  particles  of  which  were  so  small  that  they 
could  not  be  defined  clearly  with  No.  8 of  Hartnack. 
The  delicate  layer  of  protoplasm  lining  their  walls 
was  in  some  cases  a little  shrunk.  On  three  occasions 
the  above  small  masses  of  matter  were  observed  and 
sketched  at  short  intervals  of  time ; and  they  certainly 
changed  their  positions  relatively  to  each  other  and 
to  the  walls  of  the  arms.  Separate  masses  sometimes 
became  confluent,  and  then  again  divided.  A single 
little  mass  would  send  out  a projection,  which  after  a 
time  separated  itself.  Hence  there  could  be  no  doubt 
that  these  masses  consisted  of  protoplasm.  Bearing 
in  mind  that  many  clean  bladders  were  examined  with 
equal  care,  and  that  these  presented  no  such  appear- 
ance, we  may  confidently  believe  that  the  protoplasm 
in  the  above  cases  had  been  generated  by  the  absorp- 
tion of  nitrogenous  matter  from  the  decaying  animals. 
In  two  or  three  other  bladders,  which  at  first  appeared 
quite  clean,  on  careful  search  a few  processes  were 
found,  with  their  outsides  clogged  with  a little  brown 
matter,  showing  that  some  minute  animal  had  been 
captured  and  had  decayed,  and  the  arms  here  included 
a very  few  more  or  less  spherical  and  aggregated 
masses ; the  processes  in  other  parts  of  the  bladders 
being  empty  and  transparent.  On  the  other  hand,  it 
must  be  stated  that  in  three  bladders  containing  dead 
crustaceans,  the  processes  were  likewise  empty.  This 
fact  may  be  accounted  for  by  the  animals  not  having 
been  sufficiently  decayed,  or  by  time  enough  not 
having  been  allowed  for  the  generation  of  proto- 


:iHAP.  xvn.  ABSORPTION  BY  THE  QUADRIFIDS.  413 


plasm,  or  by  its  subsequent  absorption  and  transference 
to  other  parts  of  the  plant.  It  will  hereafter  be  seen 
that  in  three  or  four  other  species  of  Utricularia  the 
quadrifid  processes  in  contact  with  decaying  animals 
likewise  contained  aggregated  masses  of  protoplasm. 

On  the  Ahsorjption  of  certain  Fluids  hy  the  Quadrifid 
and  Bifid  Processes. — These  experiments  were  tried  to 
ascertain  whether  certain  fluids,  which  seemed  adapted 
for  the  purpose,  would  produce  the  same  effects  on 
the  processes  as  the  absorption  of  decayed  animal 
matter.  Such  experiments  are,  however,  troublesome ; 
for  it  is  not  suflScient  merely  to  place  a branch  in 
the  fluid,  as  the  valve  shuts  so  closely  that  the  fluid 
apparently  does  not  enter  soon,  if  at  all.  Even  when 
bristles  were  pushed  into  the  orifices,  they  were  in 
several  cases  wrapped  so  closely  round  by  the  thin 
flexible  edge  of  the  valve  that  the  fluid  was  appa- 
rently excluded  ; so  that  the  experiments  tried  in  this 
manner  are  doubtful  and  not  worth  giving.  The  best 
plan  would  have  been  to  puncture  the  bladders,  but 
I did  not  think  of  this  till  too  late,  excepting  in  a few 
cases.  In  all  such  trials,  however,  it  cannot  be  ascer- 
tained positively  that  the  bladder,  though  translucent, 
does  not  contain  some  minute  animal  in  the  last  stage 
of  decay.  Therefore  most  of  my  experiments  were 
made  by  cutting  bladders  longitudinally  into  two  ; the 
quadrifids  were  examined  with  No.  8 of  Hartnack, 
then  irrigated,  whilst  under  the  covering  glass,  with 
a few  drops  of  the  fluid  under  trial,  kept  in  a damp 
chamber,  and  re-examined  after  stated  intervals  of 
time  with  the  same  power  as  before. 

Four  bladders  were  first  tried  as  a control  experiment,  in 
the  manner  just  described,  in  a solution  of  one  part  of  gum 
arabic  to  218  of  water,  and  two  bladders  in  a solution  of  one 
part  of  sugar  to  437  of  water;  and  in  neither  case  was  any 


414 


UTRICULARIA  NEGLECTA. 


Chap.  XVII. 


change  perceptible  in  the  qnadrifids  or  bifids  after  21  hrs. 
Four  bladders  were  then  treated  in  the  same  manner  with  a 
solution  of  one  part  of  nitrate  of  ammonia  to  437  of  water,  and 
re-examined  after  21  hrs.  In  two  of  these  the  qnadrifids  now 
appeared  full  of  very  finely  granular  matter,  and  their  proto- 
plasmic lining  or  primordial  utricle  was  a little  shrunk.  In  the 
third  bladder,  the  qnadrifids  included  distinctly  visible  granules, 
and  the  primordial  utricle  was  a little  shrunk  after  only  8 hrs. 
In  the  fourth  bladder  the  primordial  utricle  in  most  of  the 
processes  was  here  and  there  thickened  into  little,  irregular, 
yellowish  specks;  and  from  the  gradations  which  could  be 
traced  in  this  and  other  cases,  these  specks  appear  to  give  rise 
to  the  larger  free  granules  contained  within  some  of  the  pro- 
cesses. Other  bladders,  which,  as  far  as  could  be  judged,  had 
never  caught  any  prey,  were  punctured  and  left  in  the  same 
solution  for  17  hrs. ; and  their  qnadrifids  now  contained  very 
fine  granular  matter. 

A bladder  was  bisected,  examined,  and  irrigated  with  a 
solution  of  one  part  of  carbonate  of  ammonia  to  437  of  water. 
After  8 hrs.  30  m.  the  qnadrifids  contained  a good  many  granules, 
and  the  primordial  utricle  was  somewhat  shrunk ; after  23  hrs. 
the  qnadrifids  and  bifids  contained  many  spheres  of  hyaline 
matter,  and  in  one  arm  twenty-four  such  spheres  of  moderate 
size  were  counted.  Two  bisected  bladders,  which  had  been 
previously  left  for  21  hrs.  in  the  solution  of  gum  (one  part  to 
218  of  water)  without  being  affected,  were  irrigated  with  the 
solution  of  carbonate  of  ammonia ; and  both  had  their  qnadrifids 
modified  in  nearly  the  same  manner  as  just  described,— one 
after  only  9 hrs.,  and  the  other  after  24  hrs.  Two  bladders 
which  appeared  never  to  have  caught  any  prey  were  punctured 
and  placed  in  the  solution ; the  qnadrifids  of  one  were  examined 
after  17  hrs.,  and  found  slightly  opaque ; the  qnadrifids  of  the 
other,  examined  after  45  hrs.,  had  their  primordial  utricles  more 
or  less  shrunk  with  thickened  yellowish  specks,  like  those  due 
to  the  action  of  nitrate  of  ammonia.  Several  uninjured  bladders 
were  left  in  the  same  solution,  as  well  as  -i  a weaker  solution 
of  one  part  to  1750  of  water,  or  1 gr.  to  4 oz. ; and  after  two 
days  the  qnadrifids  were  more  or  less  opaque,  with  their  con- 
tents finely  granular ; but  whether  the  solution  had  entered  by 
the  orifice,  or  had  been  absorbed  from  the  outside,  I know  not. 

Two  bisected  bladders  were  irrigated  with  a solution  of  one 
part  of  urea  to  218  of  water ; but  when  this  solution  was  em- 
ployed, I forgot  that  it  had  been  kept  for  some  days  in  a warm 
room,  and  had  therefore  probably  generated  ammonia ; anyhow 


Chap.  XVII.  ABSORPTION  BY  THE  QUADRIFIDS.  415 


the  quadrifids  were  affected  after  21  hrs.  as  if  a solution  of  car- 
bonate of  ammonia  had  been  nsed ; for  the  primordial  utricle 
was  thickened  in  specks,  which  seemed  to  graduate  into  separate 
granules.  Three  bisected  bladders  were  also  irrigated  with  a 
fresh  solution  of  urea  of  the  same  strength;  their  quadrifids 
after  21  hrs.  were  much  less  affected  than  in  the  former  case ; 
nevertheless,  the  primordial  utricle  in  some  of  the  arms  was 
a little  shrunk,  and  in  others  was  divided  into  two  almost 
symmetrical  sacks. 

Three  bisected  bladders,  after  being  examined,  were  irrigated 
with  a putrid  and  very  offensive  infusion  of  raw  meat.  After 
23  hrs.  the  quadrifids  and  bifids  in  all  three  specimens  abounded 
with  minute,  hyaline,  spherical  masses;  and  some  of  their 
primordial  utricles  were  a little  shrunk.  Three  bisected  blad- 
ders were  also  irrigated  with  a fresh  infusion  of  raw  meat ; and 
to  my  surprise  the  quadrifids  in  one  of  them  appeared,  after 
23  hrs.,  finely  granular,  with  their  primordial  utricles  somewhat 
shrunk  and  marked  with  thickened  yellowish  specks;  so  that 
they  had  been  acted  on  in  the  same  manner  as  by  the  putrid 
infusion  or  by  the  salts  of  ammonia.  In  the  second  bladder 
some  of  the  quadrifids  were  similarly  acted  on,  though  to  a 
very  slight  degree;  whilst  the  third  bladder  was  not  at  all 
affected. 

From  these  experiments  it  is  clear  that  the  quad- 
rifid  and  bifid  processes  have  the  power  of  absorbing 
carbonate  and  nitrate  of  ammonia,  and  matter  of 
some  kind  from  a putrid  infusion  of  meat.  Salts  of 
ammonia  were  selected  for  trial,  as  they  are  known 
to  be  rapidly  generated  by  the  decay  of  animal 
matter  in  the  presence  of  air  and  water,  and  would 
therefore  be  generated  within  the  bladders  contain- 
ing captured  prey.  The  effect  produced  on  the  pro- 
cesses by  these  salts  and  by  a putrid  infusion  of  raw 
meat  differs  from  that  produced  by  the  decay  of  the 
naturally  captured  animals  only  in  the  aggregated 
masses  of  protoplasm  being  in  the  latter  case  of  larger 
size ; but  it  is  probable  that  the  fine  granules  and 
small  hyaline  spheres  produced  by  the  solutions  would 
coalesce  into  larger  masses,  with  lime  enough  allowed. 


416 


UTRICULAEIA  NEGLECTA. 


Chap.  XVII. 


We  haye  seen  with  Drosera  that  the  first  effect  of  a 
weak  solution  of  carbonate  of  ammonia  on  the  cell- 
contents  is  the  production  of  the  finest  granules,  which 
afterwards  aggregate  into  larger,  more  or  less  rounded, 
masses ; and  that  the  granules  in  the  layer  of  protoplasm 
which  flows  round  the  walls  ultimately  coalesce  with 
these  masses.  Changes  of  this  nature  are,  however, 
far  more  rapid  in  Drosera  than  in  Utricularia.  Since 
the  bladders  have  no  power  of  digesting  albumen, 
cartilage,  or  roast  meat,  I was  surprised  that  matter 
was  absorbed,  at  least  in  one  case,  from  a fresh  infusion 
of  raw  meat.  I was  also  surprised,  from  what  we  shall 
presently  see  with  respect  to  the  glands  round  the 
orifice,  that  a fresh  solution  of  urea  produced  only  a 
moderate  effect  on  the  quadrifids. 

As  the  quadrifids  are  developed  from  papillae  which 
at  first  closely  resemble  those  on  the  outside  of  the 
bladders  and  on  the  surfaces  of  the  leaves,  I may  here 
state  that  the  two  hemispherical  cells  with  which  these 
latter  papillae  are  crowned,  and  which  in  their  natural 
state  are  perfectly  transparent,  likewise  absorb  car- 
bonate and  nitrate  of  ammonia  ; for,  after  an  immersion 
of  23  hrs.  in  solutions  of  one  part  of  both  these  salts 
to  437  of  water,  their  primordial  utricles  were  a little 
shrunk  and  of  a pale  brown  tint,  and  sometimes  finely 
granular.  The  same  result  followed  from  the  immersion 
of  a whole  branch  for  nearly  three  days  in  a solution 
of  one  part  of  the  carbonate  to  1750  of  water.  The 
grains  of  chlorophyll,  also,  in  the  cells  of  the  leaves 
on  this  branch  became  in  many  places  aggregated 
into  little  green  masses,  which  were  often  connected 
together  by  the  finest  threads. 

On  the  Absorption  of  certain  Fluids  hj  the  Glands  on 
the  Valve  and  Collar, — The  glands  round  the  orifices  of 
bladders  which  are  still  young,  or  which  have  been 


Chap.  XVIL 


ABSORPTION  BY  THE  GLANDS. 


417 


long  kept  in  moderately  pure  water,  are  colourless; 
and  their  primordial  utricles  are  only  slightly  or 
hardly  at  all  granular.  But  in  the  greater  number  of 
plants  in  a state  of  nature — and  we  must  remember 
that  they  generally  grow  in  very  foul  water  — and 
with  plants  kept  in  an  aquarium  in  foul  water,  most 
of  the  glands  were  of  a pale  brownish  tint ; their  prim- 
ordial utricles  were  more  or  less  shrunk,  sometimes 
ruptured,  with  their  contents  often  coarsely  granular 
or  aggregated  into  little  masses.  That  this  state  of 
the  glands  is  due  to  their  having  absorbed  matter  from 
the  surrounding  water,  I cannot  doubt ; for,  as  we  shall 
immediately  see,  nearly  the  same  results  follow  from 
their  immersion  for  a few  hours  in  various  solutions. 
Nor  is  it  probable  that  this  absorption  is  useless, 
seeing  that  it  is  almost  universal  with  plants  growing 
in  a state  of  nature,  excepting  when  the  water  is  re- 
markably pure. 

The  pedicels  of  the  glands  which  are  situated  close 
to  the  slit-like  orifice,  both  those  on  the  valve  and  on 
the  collar,  are  short ; whereas  the  pedicels  of  the  more 
distant  glands  are  much  elongated  and  project  inwards. 
The  glands  are  thus  well  placed  so  to  be  washed  by 
any  fluid  coming  out  of  the  bladder  through  the 
orifice.  The  valve  fits  so  closely,  judging  from  the 
result  of  immersing  uninjured  bladders  in  various 
solutions,  that  it  is  doubtful  whether  any  putrid  fluid 
habitually  passes  outwards.  But  we  must  remember 
that  a bladder  generally  captures  several  animals ; and 
that  each  time  a fresh  animal  enters,  a puff  of  foul 
water  must  pass  out  and  bathe  the  glands.  Moreover, 
1 have  repeatedly  found  that,  by  gently  pressing  blad- 
ders which  contained  air,  minute  bubbles  were  driven 
out  through  the  orifice;  and  if  a bladder  is  laid  on 
olotting  paper  and  gently  pressed,  water  oozes  out. 


UTKICULARIA  NEGLECTA. 


Chap.  XVII. 


418 

In  this  latter  case,  as  soon  as  the  pressure  is  relaxed,  air 
is  drawn  in,  and  the  bladder  recovers  its  proper  form. 
If  it  is  now  placed  under  water  and  again  gently 
pressed,  minute  bubbles  issue  from  the  orifice  and 
nowhere  else,  showing  that  the  walls  of  the  bladder 
have  not  been  ruptured.  I mention  this  because  Cohn 
quotes  a statement  by  Treviranus,  that  air  cannot  be 
forced  out  of  a bladder  without  rupturing  it.  We  may 
therefore  conclude  that  whenever  air  is  secreted  within 
a bladder  already  full  of  water,  some  water  will  be 
slowly  driven  out  through  the  orifice.  Hence  I can 
hardly  doubt  that  the  numerous  glands  crowded  round 
the  orifice  are  adapted  to  absorb  matter  from  the 
putrid  water,  which  will  occasionally  escape  from 
bladders  including  decayed  animals. 

In  order  to  test  this  conclusion,  I experimented  with  various 
solutions  on  the  glands.  As  in  the  case  of  the  quadrifids,  salts 
of  ammonia  were  tried,  since  these  are  generated  by  the  final 
decay  of  animal  matter  under  water.  Unfortunately  the  glands 
cannot  be  carefully  examined  whilst  attached  to  the  bladders 
in  their  entire  state.  Their  summits,  therefore,  including  the 
valve,  collar,  and  antennae,  were  sliced  off,  and  the  condition 
of  the  glands  observed ; they  were  then  irrigated,  whilst  beneath 
a covering  glass,  with  the  solutions,  and  after  a time  re-ex- 
amined with  the  same  power  as  before,  namely  No.  8 of  Hart- 
nack.  The  following  experiments  were  thus  made. 

As  a control  experiment  solutions  of  one  part  of  white  sugar 
and  of  one  part  of  gum  to  218  of  water  were  first  used,  to  see 
whether  these  produced  any  change  in  the  glands.  It  was 
also  necessary  to  observe  whether  the  glands  were  affected  by 
the  summits  of  the  bladders  having  been  cut  off.  The  summits 
of  four  were  thus  tried  ; one  being  examined  after  2 hrs.  30  m., 
and  the  other  three  after  23  hrs. ; but  there  was  no  marked 
change  in  the  glands  of  any  of  them. 

Two  summits  bearing  quite  colourless  glands  were  irrigated 
with  a solution  of  carbonate  of  ammonia  of  the  same  strength 
(viz.  one  part  to  218  of  water),  and  in  5 m.  the  primordial 
utricles  of  most  of  the  glands  were  somewhat  contracted ; they 
were  also  thickened  in  specks  or  patches,  and  had  assumed  a pale 


Chap.  XVIL  ABSORPTION  BY  THE  GLANDS. 


419 


brown  tint.  When  looked  at  again  after  1 hr.  30  m.,  most  of 
them  presented  a somewhat  different  appearance.  A third 
specimen  was  treated  with  a weaker  solution  of  one  part  of  the 
carbonate  to  437  of  water,  and  after  1 hr.  the  glands  were  pale 
brown  and  contained  numerous  granules. 

Four  summits  were  irrigated  with  a solution  of  one  part  of 
nitrate  of  ammonia  to  437  of  water.  One  was  examined  after 
15  m.,  and  the  glands  seemed  affected ; after  1 hr.  10  m.  there 
was  a greater  change,  and  the  primordial  utricles  in  most  of 
them  were  somewhat  shrunk,  and  included  many  granules. 
In  the  second  specimen,  the  primordial  utricles  were  consider- 
ably shrunk  and  brownish  after  2 hrs.  Similar  effects  were 
observed  in  the  two  other  specimens,  but  these  were  not  ex- 
amined until  21  hrs.  had  elapsed.  The  nuclei  of  many  of 
the  glands  apparently  had  increased  in  size.  Five  bladders 
on  a branch,  which  had  been  kept  for  a long  time  in  mode- 
rately pure  water,  were  cut  off  and  examined,  and  their  glands 
found  very  little  modified.  The  remainder  of  this  branch  was 
placed  in  the  solution  of  the  nitrate,  and  after  21  hrs.  two  blad- 
ders were  examined,  and  all  their  glands  were  brownish,  with 
their  primordial  utricles  somewhat  shrunk  and  finely  granular. 

The  summit  of  another  bladder,  the  glands  of  which  were  in  a 
beautifully  clear  condition,  was  irrigated  with  a few  drops  of 
a mixed  solution  of  nitrate  and  phosphate  of  ammonia,  each 
of  one  part  to  437  of  water.  After  2 hrs.  some  few  of  the 
glands  were  brownish.  After  8 hrs.  almost  all  the  oblong  glands 
were  brown  and  much  more  opaque  than  they  were  before; 
their  primordial  utricles  were  somewhat  shrunk  and  contained  a 
little  aggregated  granular  matter.  The  spherical  glands  were 
still  white,  but  their  utricles  were  broken  up  into  three  or 
four  small  hyaline  spheres,  with  an  irregularly  contracted  mass 
in  the  middle  of  the  basal  part.  These  smaller  spheres  changed 
their  forms  in  the  course  of  a few  hours,  and  some  of  them 
disappeared.  By  the  next  morning,  after  23  hrs.  30  m.,  they 
had  all  disappeared,  and  the  glands  were  brown ; their  utricles 
now  formed  a globular  shrunken  mass  in  the  middle.  The 
utricles  of  the  oblong  glands  had  shrunk  very  little,  but 
their  contents  were  somewhat  aggregated.  Lastly,  the  summit 
of  a bladder  which  had  been  previously  irrigated  for  21  hrs. 
with  a solution  of  one  part  of  sugar  to  218  of  water  without 
being  affected,  was  treated  with  the  above  mixed  solution ; and 
after  8 hrs.  30  m.  all  the  glands  became  brown,  with  their 
primordial  utricles  slightly  shrunk. 

Four  summits  were  irrigated  with  a putrid  infusion  of  raw 


420 


UTRICULAEIA  NEGLECTA. 


Chap.  XVn. 


meat.  No  change  in  the  glands  was  observable  for  some  hours, 
but  after  24  hrs.  most  of  them  had  become  brownish,  and  more 
opaque  and  granular  than  they  were  before.  In  these  speci- 
mens, as  in  those  irrigated  with  the  salts  of  ammonia,  the 
nuclei  seemed  to  have  increased  both  in  size  and  solidity,  but 
they  were  not  measured.  Five  summits  were  also  irrigated 
with  a fresh  infusion  of  raw  meat  ; three  of  these  were  not  at 
all  affected  in  24  hrs.,  but  the  glands  of  the  other  two  had 
perhaps  becx)me  more  granular.  One  of  the  specimens  which 
was  not  affected  was  then  irrigated  with  the  mixed  solution  of 
the  nitrate  and  phosphate  of  ammonia,  and  after  only  25  m. 
the  glands  contained  from  four  or  five  to  a dozen  granules. 
After  six  additional  hours  their  primordial  utricles  were  greatly 
shrunk. 

The  summit  of  a bladder  was  examined,  and  all  the  glands 
found  colourless,  with  their  primordial  utricles  not  at  all 
shrunk ; yet  many  of  the  oblong  glands  contained  granules  just 
resolvable  with  No.  8 of  Hartnack.  It  was  then  irrigated  with 
a few  drops  of  a solution  of  one  part  of  urea  to  218  of  water. 
After  2 hrs.  25  m.  the  spherical  glands  were  still  colourless ; 
whilst  the  oblong  and  two-armed  ones  were  of  a brownish  tint, 
and  their  primordial  utricles  much  shrunk,  some  containing 
distinctly  visible  granules.  After  9 hrs.  some  of  the  spherical 
glands  were  brownish,  and  the  oblong  glands  were  still  more 
changed,  but  they  contained  fewer  separate  granules;  their 
nuclei,  on  the  other  hand,-  appeared  larger,  as  if  they  had 
absorbed  the  granules.  After  23  hrs.  all  the  glands  were 
brown,  their  primordial  utricles  greatly  shrunk,  and  in  many 
cases  ruptured. 

A bladder  was  now  experimented  on,  which  was  already 
somewhat  affected  by  the  surrounding  water ; for  the  spherical 
glands,  though  colourless,  had  their  primordial  utricles  slightly 
shrunk;  and  the  oblong  glands  were  brownish,  with  their 
utricles  much,  but  irregularly,  shrunk.  The  summit  was 
treated  with  the  solution  of  urea,  but  was  little  affected  by  it  in 
9 hrs.;  nevertheless,  after  23  hrs.  the  spherical  glands  were 
brown,  with  their  utricles  more  shrunk;  several  of  the  other 
glands  were  still  browner,  with  their  utricles  contracted  into 
irregular  little  masses. 

Two  other  summits,  with  their  glands  colourless  and  their 
utricles  not  shrunk,  were  treated  with  the  same  solution  of 
urea.  After  5 hrs.  many  of  the  glands  presented  a shade  of 
brown,  with  their  utricles  slightly  shrunk.  After  20  hrs. 
40  m.  some  few  of  them  were  quite  brown,  and  contained 


Chap.  XVII. 


SUMMAEY  ON  ABSORPTION. 


421 


irregularly  aggregated  masses;  others  were  still  colourless, 
though  their  utricles  were  shrunk;  but  the  greater  number 
were  not  much  affected.  This  was  a good  instance  of  how 
unequally  the  glands  on  the  same  bladder  are  sometimes 
affected,  as  likewise  often  occurs  with  plants  growing  in  foul 
water.  Two  other  summits  were  treated  with  a solution  which 
had  been  kept  during  several  days  in  a warm  room,  and  their 
glands  were  not  at  all  affected  when  examined  after  21  hrs. 

A weaker  solution  of  one  part  of  urea  to  437  of  water  was  next 
tried  on  six  summits,  all  carefully  examined  before  being  irrigated. 
The  first  was  re-examined  after  8 hrs.  30  m.,  and  the  glands, 
including  the  spherical  ones,  were  brown ; many  of  the  oblong 
glands  having  their  primordial  utricles  much  shrunk  and  in- 
cluding granules.  The  second  summit,  before  being  irrigated, 
had  been  somewhat  affected  by  the  surrounding  water,  for  the 
spherical  glands  were  not  quite  uniform  in  appearance ; and  a 
few  of  the  oblong  ones  were  brown,  with  their  utricles  shrunk. 
Of  the  oblong  glands,  those  which  were  before  colourless,  be- 
came brown  in  3 hrs.  12  m.  after  irrigation,  with  their  utricles 
slightly  shrunk.  The  spherical  glands  did  not  become  brown, 
but  their  contents  seemed  changed  in  appearance,  and  after 
23  hrs.  still  more  changed  and  granular.  Most  of  the  oblong 
glands  were  now  dark  brown,  but  their  utricles  were  not 
greatly  shrunk.  The  four  other  specimens  were  examined  after 
3 hrs.  30  m.,  after  4 hrs.,  and  9 hrs. ; a brief  account  of  their 
condition  will  be  sufficient.  The  spherical  glands  were  not 
brown,  but  some  of  them  were  finely  granular.  Many  of  the 
oblong  glands  were  brown ; and  these,  as  well  as  others  which 
still  remained  colourless,  had  their  utricles  more  or  less  shrunk, 
some  of  them  including  small  aggregated  masses  of  matter. 

Summary  of  the  Observations  on  Absorption. — From 
the  facts  now  given  there  can  be  no  doubt  that  the 
variously  shaped  glands  on  the  valve  and  round  the 
collar  have  the  power  of  absorbing  matter  from  weak 
solutions  of  certain  salts  of  ammonia  and  urea,  and 
from  a putrid  infusion  of  raw  meat.  Prof.  Cohn 
believes  that  they  secrete  slimy  matter ; but  I was 
not  able  to  perceive  any  trace  of  such  action,  ex- 
cepting that,  after  immersion  in  alcohol,  extremely 
fine  lines  could  sometimes  be  seen  radiating  from  their 


422  UTRICULARIA  NEGLECTA.  Chap.  XYH. 

surfaces.  The  glands  are  variously  affected  by  absorp- 
tion ; they  often  become  of  a brown  colour ; sometimes 
they  contain  very  fine  granules,  or  moderately  sized 
grains,  or  irregularly  aggregated  little  masses ; some- 
times the  nuclei  appear  to  have  increased  in  size  ; the 
primordial  utricles  are  generally  more  or  less  shrunk 
and  sometimes  ruptured.  Exactly  the  same  changes 
may  be  observed  in  the  glands  of  plants  growing 
and  flourishing  in  foul  water.  The  spherical  glands 
are  generally  affected  rather  differently  from  the 
oblong  and  two-armed  ones.  The  former  do  not  so 
commonly  become  brown,  and  are  acted  on  more 
slowly.  We  may  therefore  infer  that  they  differ  some- 
what in  their  natural  functions. 

It  is  remarkable  how  unequally  the  glands  on  the 
bladders  on  the  same  branch,  and  even  the  glands 
of  the  same  kind  on  the  same  bladder,  are  affected  by 
the  foul  water  in  which  the  plants  have  grown,  and  by 
the  solutions  which  were  employed.  In  the  former 
case  I presume  that  this  is  due  either  to  little  currents 
bringing  matter  to  some  glands  and  not  to  others,  or 
to  unknown  differences  in  their  constitution.  When 
the  glands  on  the  same  bladder  are  differently  affected 
by  a solution,  w^e  may  suspect  that  some  of  them 
had  previously  absorbed  a small  amount  of  matter 
from  the  water.  However  this  may  be,  we  have 
seen  that  the  glands  on  the  same  leaf  of  Drosera  are 
sometimes  very  unequally  affected,  more  especially 
when  exposed  to  certain  vapours. 

If  glands  which  have  already  become  brown,  with 
their  primordial  utricles  shrunk,  are  irrigated  with 
one  of  the  effective  solutions,  they  are  not  acted  on, 
or  only  slightly  and  slowly.  If,  however,  a gland 
contains  merely  a few  coarse  granules,  this  does  not 
prevent  a solution  from  acting.  I have  never  seen 


Chap.  XVn. 


SUMMARY  ON  ABSORPTION. 


423 


any  appearance  making  it  probable  that  glands  which 
have  been  strongly  affected  by  absorbing  matter  of 
any  kind  are  capable  of  recovering  their  pristine, 
colourless,  and  homogeneous  condition,  and  of  regain- 
ing the  power  of  absorbing. 

From  the  nature  of  the  solutions  which  were  tried, 
I presume  that  nitrogen  is  absorbed  by  the  glands; 
but  the  modified,  brownish,  more  or  less  shrunk,  and 
aggregated  contents  of  the  oblong  glands  were  never 
seen  by  me  or  by  my  son  to  undergo  those  spon- 
taneous changes  of  form  characteristic  of  protoplasm. 
On  the  other  hand,  the  contents  of  the  larger 
spherical  glands  often  separated  into  small  hyaline 
globules  or  irregularly  shaped  masses,  which  changed 
their  forms  very  slowly  and  ultimately  coalesced, 
forming  a central  shrunken  mass.  Whatever  may  be 
the  nature  of  the  contents  of  the  several  kinds  of 
glands,  after  they  have  been  acted  on  by  foul  water 
or  by  one  of  the  nitrogenous  solutions,  it  is  probable 
that  the  matter  thus  generated  is  of  service  to  the 
plant,  and  is  ultimately  transferred  to  other  parts. 

The  glands  apparently  absorb  more  quickly  than  do 
the  quadrifid  and  bifid  processes;  and  on  the  view 
above  maintained,  namely  that  they  absorb  matter 
from  putrid  water  occasionally  emitted  from  the 
bladder?,  they  ought  to  act  more  quickly  than  the 
processes ; as  these  latter  remain  in  permanent  con- 
tact with  captured  and  decaying  animals. 

Finally,  the  conclusion  to  which  we  are  led  by 
the  foregoing  experiments  and  observations  is  that 
the  bladders  have  no  power  of  digesting  animal 
matter,  though  it  appears  that  the  quadrifids  are 
somewhat  affected  by  a fresh  infusion  of  raw  meat. 
It  is  certain  that  the  processes  within  the  bladders, 
and  the  glands  outside,  absorb  matter  from  salts  of 
19 


424 


UTKICULARIA  NEGLECTA. 


Chap.  XVII. 


ammonia,  from  a putrid  infusion  of  raw  moat,  and  from 
urea.  The  glands  apparently  are  acted  on  more 
strongly  by  a solution  of  urea,  and  less  strongly  by 
an  infusion  of  raw  meat,  than  are  the  processes.  The 
case  of  urea  is  particularly  interesting,  because  we 
have  seen  that  it  produces  no  effect  on  Drosera,  the 
leaves  of  which  are  adapted  to  digest  fresh  animal 
matter.  But  the  most  important  fact  of  all  is,  that 
in  the  present  and  following  species  the  quadrifid 
and  bifid  processes  of  bladders  containing  decayed 
animals  generally  include  little  masses  of  spontane- 
ously moving  protoplasm ; whilst  such  masses  are 
never  seen  in  perfectly  clean  bladders. 

Development  of  the  Bladders, — My  son  and  I spent 
much  time  over  this  subject  with  small  success.  Our 
observations  apply  to  the  present  species  and  to  TJtri- 
cularia  vulgaris^  but  were  made  chiefly  on  the  latter,  as 
the  bladders  are  twice  as  large  as  those  of  TJtricularia 
neglecta.  In  the  early  part  of  autumn  the  stems  ter- 
minate in  large  buds,  which  fall  off  and  lie  dormant 
during  the  winter  at  the  bottom.  The  young  leaves 
forming  these  buds  bear  bladders  in  various  stages  of 
early  development.  When  the  bladders  of  TJtricularia 
vulgaris  are  about  inch  (*254  mm.)  in  diameter 
(or  -2-^  in  the  case  of  TJtricularia  neglecta),  they  are 
circular  in  outline,  with  a narrow,  almost  closed,  trans- 
verse orifice,  leading  into  a hollow  filled  with  water ; 
but  the  bladders  are  hollow  when  much  under  -j-J-o  of 
an  inch  in  diameter.  The  orifices  face  inwards  or 
towards  the  axis  of  the  plant.  At  this  early  age  the 
bladders  are  flattened  in  the  plane  in  which  the  orifice 
lies,  and  therefore  at  right  angles  to  that  of  the 
mature  bladders.  They  are  covered  exteriorly  with 
papillae  of  different  sizes,  many  of  which  have  an 
elliptical  outline.  A bundle  of  vessels,  formed  of 


Chap.  XVII.  DEVELOPMENT  OF  THE  BLADDERS.  425 

simple  elongated  cells,  runs  up  the  short  footstalk, 
and  divides  at  the  base  of  the  bladder.  One  branch 
extends  up  the  middle  of  the  dorsal  surface,  and 
the  other  up  the  middle  of  the  ventral  surface.  In 
full-grown  bladders  the  ventral  bundle  divides  close 
beneath  the  collar,  and  the  two  branches  run  on  each 
side  to  near  where  the  corners  of  the  valve  unite  with 
the  collar ; but  these  branches  could  not  be  seen  in 
very  young  bladders. 

The  accompanying  figure  (fig.  23)  shows  a section, 
which  happened  to  be  strictly  medial,  through  the  foot- 
stalk and  between  the  nascent  antennse  of  a bladder 
of  TJtricularia  vulgaris,  inch 
in  diameter.  The  specimen  was 
soft,  and  the  young  valve  be- 
came separated  from  the  collar 
to  a greater  degree  than  is 
natural,  and  is  thus  represented. 

We  here  clearly  see  that  the 
valve  and  collar  are  infolded 
prolongations  of  the  walls  of  the 
bladder.  Even  at  this  early 
age,  glands  could  be  detected 
on  the  valve.  The  state  of  the 
quadrifid  processes  will  presently 
be  described.  The  antennae  at  this 
period  consist  of  minute  cellular  projections  (not  shown 
in  the  above  figure,  as  they  do  not  lie  in  the  medial 
plane),  which  soon  bear  incipient  bristles.  In  five 
instances  the  young  antennae  were  not  of  quite  equal 
length ; and  this  fact  is  intelligible  if  I am  right  in 
believing  that  they  represent  two  divisions  of  the 
leaf,  rising  from  the  end  of  the  bladder;  for,  with 
the  true  leaves,  whilst  very  young,  the  divisions  are 
never,  as  far  as  I have  seen,  strictly  opposite;  they 


Longitudinal  section  through 
a young  bladder,  7^  of  an  inch 
in  length,  with  the  orifice  too 
widely  open. 


426 


UTKICULAEIA  NEGLECTA. 


Chap.  XVIL 


must  therefore  be  developed  one  after  the  other,  and 
so  it  would  be  with  me  two  antennae. 

At  a much  earlier  age,  when  the  half  formed 
bladders  are  only  inch  (*0846  mm.)  in  diameter 
or  a little  more,  they  present  a totally  different  ap- 
pearance. One  is  represented  on  the  left  side  of  the 
accompanying  drawing  (fig.  24).  The  young  leaves 


FiO.  34. 

{Utricularia  vulgaris.) 

Young  leaf  from  a winter  bud,  showing  on  the  left  side  a bladder  in  its  earliest  stage 
of  development. 

at  this  age  have  broad  flattened  segments,  with  their 
future  divisions  represented  by  prominences,  one  of 
which  is  shown  on  the  right  side.  Now,  in  a large 
number  of  specimens  examined  by  my  son,  the  young 
bladders  appeared  as  if  formed  by  the  oblique  folding 
over  of  the  apex  and  of  one  margin  with  a prominence, 
against  the  opposite  margin.  The  circular  hollow 
between  the  infolded  apex  and  infolded  prominence 
apparently  contracts  into  the  narrow  orifice,  wherein 
the  valve  and  collar  will  be  developed ; the  bladder 
itself  being  formed  by  the  confluence  of  the  opposed 


Chap.  XVn.  DEVELOPMENT  OF  THE  BLADDEES.  427 

margins  of  the  rest  of  the  leaf.  But  strong  objections 
may  be  urged  against  this  view,  for  we  must  in  this 
case  suppose  that  the  valve  and  collar  are  developed 
asymmetrically  from  the  sides  of  the  apex  and  pro- 
minence. Moreover,  the  bundles  of  vascular  tissue 
have  to  be  formed  in  lines  quite  irrespective  of  the 
original  form  of  the  leaf.  Until  gradations  can  be 
shown  to  exist  between  this  the  earliest  state  and  a 
young  yet  perfect  bladder,  the  case  must  be  left 
doubtful. 

As  the  quadrifid  and  bifid  processes  offer  one  of  the 
greatest  peculiarities  in  the  genus,  I carefully  observed 
their  development  in  Utrieularia  neglecta.  In  bladders 
about  of  an  inch  in  diameter,  the  inner  surface 
is  studded  with  papillae,  rising  from  small  cells  at  the 
junctions  of  the  larger  ones.  These  papillae  consist  of 
a delicate  conical  protuberance,  which  narrows  into 
a very  short  footstalk,  surmounted  by  two  minute 
cells.  They  thus  occupy  the  same  relative  position, 
and  closely  resemble,  except  in  being  smaller  and 
rather  more  prominent,  the  papillae  on  the  outside  of 
the  bladders,  and  on  the  surfaces  of  the  leaves.  The 
two  terminal  cells  of  the  papillae  first  become  much 
elongated  in  a line  parallel  to  the  inner  surface  of  the 
bladder.  Next,  each  is  divided  by  a longitudinal 
partition.  Soon  the  two  half-cells  thus  formed  sepa- 
rate from  one  another ; and  we  now  have  four  cells  or 
an  incipient  quadrifid  process.  As  there  is  not  space 
for  the  two  new  cells  to  increase  in  breadth  in  their 
original  plane,  the  one  slides  partly  under  the  other. 
Their  manner  of  growth  now  changes,  and  their  outer 
sides,  instead  of  their  apices,  continue  to  grow.  The 
two  lower  cells,  which  have  slid  partly  beneath  the  two 
upper  ones,  form  the  longer  and  more  upright  pair  of 
processes ; whilst  the  two  upper  cells  form  the  shorter 


428 


UTRICULARIA  VULGARIS. 


Chap.  XVIL 


and  more  horizontal  pair;  the  fonr  together  forming 
a perfect  quadrifid.  A trace  of  the  primary  division 
between  the  two  cells  on  the  summits  of  the  papilla©  can 
still  be  seen  between  the  bases  of  the  longer  processes. 
The  development  of  the  quadriflds  is  very  liable  to 
be  arrested.  I have  seen  a bladder  3?^  of  an  inch 
in  length  including  only  primordial  papilla© ; and 
another  bladder,  about  half  its  full  size,  with  the 
quadriflds  in  an  early  stage  of  development. 

As  far  as  I could  make  out,  the  bifld  processes  are 
developed  in  the  same  manner  as  the  quadriflds, 
excepting  that  the  two  primary  terminal  cells  never 
become  divided,  and  only  increase  in  length.  The 
glands  on  the  valve  and  collar  appear  at  so  early  an 
age  that  I could  not  trace  their  development ; but 
we  may  reasonably  suspect  that  they  are  developed 
from  papilla©  like  those  on  the  outside  of  the  bladder, 
but  with  their  terminal  cells  not  divided  into  two. 
The  two  segments  forming  the  pedicels  of  the  glands 
probably  answer  to  the  conical  protuberance  and  short 
footstalk  of  the  quadrifld  and  bifld  processes.  I am 
strengthened  in  the  belief  that  the  glands  are  de- 
veloped from  papilla©  like  those  on  the  outside  of  the 
bladders,  from  the  fact  that  in  TJtricularia  ameihystina 
the  glands  extend  along  the  whole  ventral  surface 
of  the  bladder  close  to  the  footstalk. 

Utricularia  vulgaris. 

Living  plants  from  Yorkshire  were  sent  me  by  Dr.  Hooker. 
This  species  differs  from  the  last  in  the  stems  and  leaves  being 
thicker  or  coarser;  their  divisions  form  a more  acute  angle 
with  one  another;  the  notches  on  the  leaves  bear  three  or 
four  short  bristles  instead  of  one ; and  the  bladders  are  twice 
as  large,  or  about  \ of  an  inch  (5  08  mm.)  in  diameter.  In 
all  essential  respects  the  bladders  resemble  those  of  Utricularia 
neglecta^  but  the  siaes  of  the  peristome  are  perhaps  a little  more 


Chap.  XVII. 


UTRICULARIA  MINOR. 


429 


prominent,  and  always  bear,  as  far  as  I have  seen,  seven  or 
eight  long  multicellular  bristles.  There  are  eleven  long  bristles 
on  each  antenna,  the  terminal  pair  being  included.  Five 
bladders,  containing  prey  of  some  kind,  were  examined.  The 
first  included  five  Cypris,  a large  copepod  and  a Diaptomus ; 
the  second,  four  Cypris ; the  third,  a single  rather  large  crus- 
tacean; the  fourth,  six  crustaceans;  and  the  fifth,  ten.  My 
son  examined  the  quadrifid  processes  in  a bladder  containing 
the  remains  of  two  crustaceans,  and  found  some  of  them  full  of 
spherical  or  irregularly  shaped  masses  of  matter,  which  were 
observed  to  move  and  to  coalesce.  These  masses  therefore  con- 
sisted of  protoplasm. 

Utricularia  minor. 

This  rare  species  was  sent  me  in  a living  state  from  Cheshire, 
through  the  kindness  of  Mr.  John  Price.  The  leaves  and 
bladders  are  much  smaller  than  those  of  Utricularia  neglecta. 
The  leaves  bear  fewer  and  shorter  bristles,  and  the  bladders  are 
more  globular.  The  antennae,  instead  of  projecting  in  front 
of  the  bladders,  are  curled  under  the  valve,  and  are  armed  with 
twelve  or  fourteen  extremely  long 
multicellular  bristles,  generally 
arranged  in  pairs.  These,  with 
seven  or  eight  long  bristles  on 
both  sides  of  the  peristome,  form 
a sort  of  net  over  the  valve,  which 
would  tend  to  prevent  all  ani- 
mals, excepting  very  small  ones, 
entering  the  bladder.  The  valve 
and  collar  have  the  same  essential 
structure  as  in  the  two  previous 
species ; but  the  glands  are  not 
quite  so  numerous;  the  oblong 
ones  are  rather  more  elongated,  whilst  the  two- armed  ones  are 
rather  less  elongated.  The  four  bristles  which  project  obliquely 
from  the  lower  edge  of  the  valve  are  short.  Their  shortness, 
compared  with  those  on  the  valves  of  the  foregoing  species,  is 
intelligible  if  my  view  is  correct  that  they  serve  to  prevent 
too  large  animals  forcing  an  entrance  through  the  valve,  thus 
injuring  it;  for  the  valve  is  already  protected  to  a certain 
extent  by  the  incurved  antennae,  together  with  the  lateral 
bristles.  The  bifid  processes  are  like  those  in  the  previous 
species;  but  the  quadrifids  differ  in  the  four  arms  (fig.  25) 


Fig.  25. 

(^I'tricularia  minor.') 
Quadrifid  process ; greatly  enlarged. 


i30 


UTRICULAKIA  CLANDESTINA. 


Chap.  XVIL 


being  directed  to  the  same  side ; the  two  longer  ones  being 
central,  and  the  two  shorter  ones  on  the  outside. 

The  plants  were  collected  in  the  middle  of  July;  and  the 
contents  of  five  bladders,  which  from  their  opacity  seemed  full 
of  prey,  were  examined.  The  first  contained  no  less  than 
twenty-four  minute  fresh-water  crustaceans,  most  of  them  con- 
sisting of  empty  shells,  or  including  only  a few  drops  of  red  oily 
matter;  the  second  contained  twenty;  the  third,  fifteen;  the 
fourth,  ten,  some  of  them  being  rather  larger  than  usual ; and 
the  fifth,  which  seemed  stuffed  quite  full,  contained  only  seven, 
but  five  of  these  were  of  unusually  large  size.  The  prey, 
therefore,  judging  from  these  five  bladders,  consists  exclusively 
of  fresh- water  crustaceans,  most  of  which  appeared  to  be  distinct 
species  from  those  found  in  the  bladders  of  the  two  former 
species.  In  one  bladder  the  quadrifids  in  contact  with  a decay- 
ing mass  contained  numerous  spheres  of  granular  matter, 
which  slowly  changed  their  forms  and  positions. 

Utricularia  clandestina. 

This  North  American  species,  which  is  aquatic  like  the  three 
foregoing  ones,  has  been  described  by  Mrs.  Treat,  of  New  Jersey, 
whose  excellent  observations  have  already  been  largely  quoted. 
I have  not  as  yet  seen  any  full  description  by  her  of  the  structure 
of  the  bladder,  but  it  appears  to  be  lined  with  quadrifid 
processes.  A vast  number  of  captured  animals  were  found 
within  the  bladders;  some  being  crustaceans,  but  the  greater 
number  delicate,  elongated  larvae,  I suppose  of  Culicidse.  On 
some  stems,  ‘'fully  nine  out  of  every  ten  bladders  contained 
these  larvae  or  their  remains."  The  larvae  “ showed  signs  of  life 
from  twenty-four  to  thirty-six  hours  after  being  imprisoned," 
and  then  perished. 


Chap.  X VIII. 


UTRICULARIA  MONTANA. 


431 


CHAPTEE  XVIII. 

Utricularia  (continued'). 

Utricularia  montana — ‘Description  of  the  bladders  on  the  subter- 
ranean rhizomes  — Prey  captured  by  the  bladders  of  plants  under 
culture  and  in  a state  of  nature — Absorption  by  the  quadrifid  pro- 
cesses and  glands  — Tubers  serving  as  reservoirs  for  "water  — 
Various  other  species  of  Utricularia  — Polypompholyx  — Genlisea, 
different  nature  of  the  trap  for  capturing  prey  — Diversified 
methods  by  which  plants  are  nourished. 

Uteicularia  MONTANA. — This  species  inhabits  the 
tropical  parts  of  South  America,  and  is  said  to  be 
epiphytic;  but,  judging  from  the  state  of  the  roots 
(rhizomes)  of  some  dried  spe- 
cimens from  the  herbarium 
at  Kew,  it  likewise  lives  in 
earth,  probably  in  crevices 
of  rocks.  In  English  hot- 
houses it  is  grown  in  peaty 
soil.  Lady  Dorothy  Nevill 
was  so  kind  as  to  give  me 
a fine  plant,  and  I received 
another  from  Dr.  Hooker. 

The  leaves  are  entire,  instead 
of  being  much  divided,  as 
in  the  foregoing  aquatic 
species.  They  are  elongated, 
about  u inch  in  breadth,  brfnjhTberng 
and  furnished  with  a dis- 

tinct  footstalk.  The  plant  produces  numerous  colour- 
less rhizomes,  as  thin  as  threads,  which  bear  minute 
bladders,  and  occasionally  swell  into  tubers,  as  will 


Fig.  26. 

{Utricularia  montana.') 


432 


UTKICULAKIA  MONTANA. 


Chap.  XVIH. 


hereafter  be  described.  These  rhizomes  appear  ex- 
actly like  roots,  but  occasionally  throw  up  green 
shoots.  They  penetrate  the  earth  sometimes  to  the 
depth  of  more  than  2 inches ; but  when  the  plant 
grows  as  an  epiphyte,  they  must  creep  amidst  the 
mosses,  roots,  decayed  bark,  &c.,  with  which  the  trees 
of  these  countries  are  thickly  covered. 

As  the  bladders  are  attached  to  the  rhizomes,  they 
are  necessarily  subterranean.  They  are  produced  in 
extraordinary  numbers.  One  of  my  plants,  though 
young,  must  have  borne  several  hundreds  ; for  a single 
branch  out  of  an  entangled  mass  had  thirty-two,  and 
another  branch,  about  2 inches  in  length  (but  with  its 
end  and  one  side  branch  broken  off),  had  seventy-three 
bladders.*  The  bladders  are  compressed  and  rounded, 
with  the  ventral  surface,  or  that  between  the  summit 
of  the  long  delicate  footstalk  and  valve,  extremely 
short  (fig.  27).  They  are  colourless  and  almost  as 
transparent  as  glass,  so  that  they  appear  smaller  than 
they  really  are,  the  largest  being  under  the  of  an 
inch  (1*27  mm.)  in  its  longer  diameter.  They  are 
formed  of  rather  large  angular  cells,  at  the  junctions 
of  which  oblong  papillae  project,  corresponding  with 
those  on  the  surfaces  of  the  bladders  of  the  previous 
species.  Similar  papillae  abound  on  the  rhizomes,  and 
even  on  the  entire  leaves,  but  they  are  rather  broader 
on  the  latter.  Vessels,  marked  with  parallel  bars 
instead  of  by  a spiral  line,  run  up  the  footstalks,  and 


* Prof.  Oliver  has  figured  a 
plant  of  Utricularia  Jamesoniana 
(‘  Proc.  Linn.  Soc.*  vol.  iv.  p.  169) 
having  entire  leaves  and  rhizomes, 
like  those  of  our  present  species ; 
but  the  margins  of  the  terminal 
halves  of  some  of  the  leaves  are 
converted  into  bladders.  This  fact 


clearly  indicates  that  the  bladders 
on  the  rhizomes  of  the  present  and 
following  species  are  modified  seg- 
ments of  the  leaf ; and  they  are 
thus  brought  into  accordance  with 
the  bladders  attached  to  the  di- 
vided and  floating  leaves  of  the 
axjuatic  species. 


Chap.  XVIII.  STKUCTUKE  OF  THE  BLADDERS. 


433 


just  enter  tlie  bases  of  the  bladders ; but  they  do  not 
bifurcate  and  extend  up  the  dorsal  and  ventral  sur- 
faces, as  in  the  previous  species. 

The  antennae  are  of  moderate  length,  and  taper  to  a 
fine  point ; they  differ  conspicuously  from  those  before 
described,  in  not  being  armed  with  bristles.  Their 
bases  are  so  abruptly  curved  that  their  tips  generally 
rest  one  on  each  side  of  the  middle  of  the  bladder,  but 


Fig.  27. 

(JJtricularia  montana.) 
Bladder;  about  27  times  enlarged. 


sometimes  near  the  margin.  Their  curved  bases  thus 
form  a roof  over  the  cavity  in  which  the  valve  lies; 
but  there  is  always  left  on  each  side  a little  circular 
passage  into  the  cavity,  as  may  be  seen  in  the  drawing, 
as  well  as  a narrow  passage  between  the  bases  of  the 
two  antennae.  As  the  bladders  are  subterranean,  had 
it  not  been  for  the  roof,  the  cavity  in  which  the  valve 
lies  would  have  been  liable  to  be  blocked  up  with  earth 


434  UTMCULARIA  MONTANA.  Chap.  XVIIL 

and  rubbish ; so  that  the  curvature  of  the  antennae  is 
a serviceable  character.  There  are  no  bristles  on  the 
outside  of  the  collar  or  peristome,  as  in  the  foregoing 
species. 

The  valve  is  small  and  steeply  inclined,  with  its  free 
posterior  edge  abutting  against  a semicircular,  deeply 
depending  collar.  It  is  moderately  transparent,  and 
bears  two  pairs  of  short  stiff  bristles,  in  the  same 
position  as  in  the  other  species.  The  presence  of  these 
four  bristles,  in  contrast  with  the  absence  of  those  on 
the  antennsB  and  collar,  indicates  that  they  are  of 
functional  importance,  namely,  as  I believe,  to  prevent 
too  large  animals  forcing  an  entrance  through  the 
valve.  The  many  glands  of  diverse  shapes  attached 
to  the  valve  and  round  the  collar  in  the  previous 
species  are  here  absent,  with  the  exception  of  about 
a dozen  of  the  two-armed  or  transversely  elongated 
kind,  which  are  seated  near  the  borders  of  the  valve, 
and  are  mounted  on  very  short  footstalks.  These 
glands  are  only  the  -rtVo  (*019  mm.)  in 

length ; though  so  small,  they  act  as  absorbents. 
The  collar  is  thick,  stiff,  and  almost  semi-circular ; it 
is  formed  of  the  same  peculiar  brownish  tissue  as  in 
the  former  species. 

The  bladders  are  filled  with  water,  and  sometimes 
include  bubbles  of  air.  They  bear  internally  rather 
short,  thick,  quadrifid  processes  arranged  in  approxi- 
mately concentric  rows.  The  two  pairs  of  arms  of 
which  they  are  formed  differ  only  a little  in  length, 
and  stand  in  a peculiar  position  (fig.  28) ; the  two 
longer  ones  forming  one  line,  and  the  two  shorter  ones 
another  parallel  line.  Each  arm  includes  a small 
spherical  mass  of  brownish  matter,  which,  when 
crushed,  breaks  into  angular  pieces.  I have  no  doubt 
that  these  spheres  are  nuclei,  for  closely  similar  ones 


Chap.  XVIII. 


CAPTURED  ANIMALS. 


435 


are  present  in  the  cells  forming  the  walls  of  the 
bladders.  Bifid  processes,  having  rather  short  oval 
arms,  arise  in  the  usual  position  on  the  inner  side  of 
the  collar. 

These  bladders,  therefore,  resemble  in  all  essential 
respects  the  larger  ones  of  the  foregoing  species. 
They  differ  chiefly  in  the  absence  of  the  numerous 
glands  on  the  valve  and  round  the  collar,  a few  minute 
ones  of  one  kind  alone  being  present  on  the  valve. 
They  differ  more  conspicuously  in  the  absence  of  the 
long  bristles  on  the  antennae  and  on  the  outside  of 
the  collar.  The  presence  of  these  bristles  in  the  pre- 
viously mentioned  species  probably  relates  to  the 
capture  of  aquatic  animals. 


Fig.  28. 

(JJtricularia  montana.') 

One  of  the  quadrifid  processes ; much  enlarged. 

It  seemed  to  me  an  interesting  question  whether 
the  minute  bladders  of  JJtricularia  montana  served,  as  in 
the  previous  species,  to  capture  animals  living  in  the 
earth,  or  in  the  dense  vegetation  covering  the  trees  on 
which  this  species  is  epiphytic ; for  in  this  case  we 
should  have  a new  sub-class  of  carnivorous  plants, 
namely,  subterranean  feeders.  Many  bladders,  there- 
fore, were  examined,  with  the  following  results 

(1)  A small  bladder,  less  than  of  an  inch  (*847  mm.)  in  dia- 
meter, contained  a minute  mass  of  brown,  much  decayed  matter ; 
and  in  this,  a tarsus  with  four  or  five  joints,  terminating  in  a 
double  hook,  was  clearly  distinguished  under  the  microscope. 
I suspect  that  it  was  a remnant  of  one  of  the  Thysanoura.  The 
quadrifids  in  contact  with  this  decayed  remnant  contained  either 
small  masses  of  translucent,  yellowish  matter,  generally  more 


436 


UTRICULARIA  MONTANA. 


Chap.  XVIII 


or  less  globular,  or  fine  granules.  In  distant  parts  of  the  same 
bladder,  the  processes  were  transparent  %nd  quite  empty,  with 
the  exception  of  their  solid  nuclei.  My  son  made  at  short 
intervals  of  time  sketches  of  one  of  the  above  aggregated 
masses,  and  found  that  they  continually  and  completely  changed 
their  forms;  sometimes  separating  from. one  another  and  again 
coalescing.  Evidently  protoplasm  had  been  generated  by  the 
absorption  of  some  element  from  the  decaying  animal  matter. 

(2)  Another  bladder  included  a still  smaller  speck  of  decayed 
brown  matter,  and  the  adjoining  quadrifids  contained  aggre- 
gated matter,  exactly  as  in  the  last  case. 

(3)  A third  bladder  included  a larger  organism,  which  was  so 
much  decayed  that  I could  only  make  out  that  it  was  spinose  or 
hairy.  The  quadrifids  in  this  case  were  not  much  affected, 
excepting  that  the  nuclei  in  the  several  arms  differed  much  in 
size;  some  of  them  containing  two  masses  having  a similar 
appearance. 

(4)  A fourth  bladder  contained  an  articulate  organism,  for 
I distinctly  saw  the  remnant  of  a limb,  terminating  in  a hook. 
The  quadrifids  were  not  examined. 

(5)  A fifth  included  much  decayed  matter  apparently  of  some 
animal,  but  with  no  recognisable  features.  The  quadrifids  in 
contact  contained  numerous  spheres  of  protoplasm. 

(6)  Some  few  bladders  on  the  plant  which  I received  from 
Kew  were  examined;  and  in  one,  there  was  a worm-shaped 
animal  very  little  decayed,  with  a distinct  remnant  of  a similar 
one  greatly  decayed.  Several  of  the  arms  of  the  processes  in 
contact  with  these  remains  contained  two  spherical  masses,  like 
the  single  solid  nucleus  which  is  properly  found  in  each  arm. 
In  another  bladder  there  was  a minute  grain  of  quartz,  remind- 
ing me  of  two  similar  cases  with  Utricularia  neglecta. 

As  it  appeared  probable  that  this  plant  would  capture  a 
greater  number  of  animals  in  its  native  country  than  under 
culture,  I obtained  permission  to  remove  small  portions  of  the 
rhizomes  from  dried  specimens  in  the  herbarium  at  Kew.  I did 
not  at  first  find  out  that  it  was  advisable  to  soak  the  rhizomes 
for  two  or  three  days,  and  that  it  was  necessary  to  open  the 
bladders  and  spread  eut  their  contents  on  glass ; as  from  their 
state  of  decay  and  from  having  been  dried  and  pressed,  their 
nature  could  not  otherwise  be  well  distinguished.  Several 
bladders  on  a plant  which  had  grown  in  black  earth  in  New 
Granada  were  first  examined;  and  four  of  these  included 
remnants  of  animals.  The  first  contained  a hairy  Acarus,  so 
much  decayed  that  nothing  was  left  except  its  transparent  coat; 


Chap.  XVm. 


ABSOKPTION. 


437 


also  a yellow  chitinous  head  of  some  animal  with  an  internal 
fork,  to  which  the  oesophagus  was  suspended,  but  I could  see 
no  mandibles;  also  the  double  hook  of  the  tarsus  of  some 
animal;  also  an  elongated  greatly  decayed  animal;  and  lastly, 
a curious  flask-shaped  organism,  having  the  walls  formed  of 
rounded  cells.  Professor  Claus  has  looked  at  this  latter  organism, 
and  thinks  that  it  is  the  shell  of  a rhizopod,  probably  one  of  the 
Arcellidae.  In  this  bladder,  as  well  as  in  several  others,  there 
were  some  unicellular  Algae,  and  one  multicellular  Alga,  which 
no  doubt  had  lived  as  intruders. 

A second  bladder  contained  an  Acarus  much  less  decayed 
than  the  former  one,  with  its  eight  legs  preserved ; as  well  as 
remnants  of  several  other  articulate  animals.  A third  bladder 
contained  the  end  of  the  abdomen  with  the  two  hinder  limbs 
of  an  Acarus,  as  I believe.  A fourth  contained  remnants  of  a 
distinctly  articulated  bristly  animal,  and  of  several  other  organ- 
isms, as  well  as  much  dark  brown  organic  matter,  the  nature 
of  which  could  not  be  made  out. 

Some  bladders  from  a plant,  which  had  lived  as  an  epiphyte 
in  Trinidad,  in  the  West  Indies,  were  next  examined,  but  not 
so  carefully  as  the  others;  nor  had  they  been  soaked  long 
enough.  Pour  of  them  contained  much  brown,  translucent, 
granular  matter,  apparently  organic,  but  with  no  distinguish- 
able parts.  The  quadrifids  in  two  were  brownish,  with  their 
contents  granular ; and  it  was  evident  that  they  had  absorbed 
matter.  In  a fifth  bladder  there  was  a flask-shaped  organism, 
like  that  above  mentioned.  A sixth  contained  a very  long, 
much  decayed,  worm-shaped  animal.  Lastly,  a seventh  bladder 
contained  an  organism,  but  of  what  nature  could  not  be  dis- 
tinguished. 

Only  one  experiment  was  tried  on  the  qnadrifid  pro- 
cesses and  glands  with  reference  to  their  power  of 
absorption.  A bladder  was  punctured  and  left  for 
24  hrs.  in  a solution  of  one  part  of  urea  to  437  of 
water,  and  the  quadrifid  and  bifid  processes  were  found 
much  affected.  In  some  arms  there  was  only  a single 
symmetrical  globular  mass,  larger  than  the  proper 
nucleus,  and  consisting  of  yellowish  matter,  generally 
translucent  but  sometimes  granular;  in  others  there 
were  two  masses  of  different  sizes,  one  large  and  the 


138 


UTRICULARIA  MONTANA. 


Chap.  XVIII 


other  small;  and  in  others  there  were  irregularly 
shaped  globules ; so  that  it  appeared  as  if  the  limpid 
contents  of  the  processes,  owing  tc  the  absorption  of 
matter  from  the  solution,  had  become  aggregated 
sometimes  round  the  nucleus,  and  sometimes  into  sepa- 
rate masses ; and  that  these  then  tended  to  coalesce. 
The  primordial  utricle  or  protoplasm  lining  the  pro- 
cesses was  also  thickened  here  and  there  into  irregular 
and  variously  shaped  specks  of  yellowish  translucent 
matter,  as  occurred  in  the  case  of  TItricularia  neglecta 
under  similar  treatment.  These  specks  apparently  did 
not  change  their  forms. 

The  minute  two-armed  glands  on  the  valve  were 
also  affected  by  the  solution ; for  they  now  contained 
several,  sometimes  as  many  as  six  or  eight,  almost 
spherical  masses  of  translucent  matter,  tinged  with 
yellow,  which  slowly  changed  their  forms  and  posi- 
tions. Such  masses  were  never  observed  in  these  glands 
in  their  ordinary  state.  We  may  therefore  infer  that 
they  serve  for  absorption.  Whenever  a little  water  is 
expelled  from  a bladder  containing  animal  remains 
(by  the  means  formerly  specified,  more  especially  by 
the  generation  of  bubbles  of  air),  it  will  fill  the  cavity 
in  which  the  valve  lies ; and  thus  the  glands  will  be 
able  to  utilise  decayed  matter  which  otherwise  would 
have  been  wasted. 

Finally,  as  numerous  minute  animals  are  captured 
by  this  plant  in  its  native  country  and  when  culti- 
vated, there  can  be  no  doubt  that  the  bladders,  though 
so  small,  are  far  from  being  in  a rudimentary  con- 
dition ; on  the  contrary,  they  are  highly  efficient 
traps.  Nor  can  there  be  any  doubt  that  matter  is 
absorbed  from  the  decayed  prey  by  the  quadrifid  and 
bifid  processes,  and  that  protoplasm  is  thus  generated. 
What  tempts  animals  of  such  diverse  kinds  to  enter 


Chap.  XVm. 


RESERVOIRS  FOR  WATER. 


439 


the  cavity  beneath  the  bowed  antennsB,  and  then  force 
their  way  through  the  little  slit-like  orifice  between 
the  valve  and  collar  into  the  bladders  filled  with 
water,  I cannot  conjecture. 

Tubers. — These  organs,  one  of  which  is  represented 
in  a previous  figure  (fig.  26)  of  the  natural  size, 
deserve  a few  remarks.  Twenty  were  found  on  the 
rhizomes  of  a single  plant,  but  they  cannot  be  strictly 
counted ; for,  besides  the  twenty,  there  were  all  pos- 
sible gradations  between  a short  length  of  a rhizome 
just  perceptibly  swollen  and  one  so  much  swollen  that 
it  might  be  doubtfully  called  a tuber.  When  well 
developed,  they  are  oval  and  symmetrical,  more  so 
than  appears  in  the  figure.  The  largest  which  I 
saw  was  1 inch  (25*4  mm.)  in  length  and  *45  inch 
(11*43  mm.)  in  breadth.  They  commonly  lie  near 
the  surface,  but  some  are  buried  at  the  depth  of 
2 inches.  The  buried  ones  are  dirty  white,  but  those 
partly  exposed  to  the  light  become  greenish  from  the 
development,  of  chlorophyll  in  their  superficial  cells. 
They  terminate  in  a rhizome,  but  this  sometimes 
decays  and  drops  oif.  They  do  not  contain  any  air, 
and  they  sink  in  water ; their  surfaces  are  covered 
with  the  usual  papillae.  The  bundle  of  vessels  which 
runs  up  each  rhizome,  as  soon  as  it  enters  the  tuber, 
separates  into  three  distinct  bundles,  which  reunite 
at  the  opposite  end.  A rather  thick  slice  of  a tuber  is 
almost  as  transparent  as  glass,  and  is  seen  to  consist 
of  large  angular  cells,  full  of  water  and  not  containing 
starch  or  any  other  solid  matter.  Some  slices  were 
left  in  alcohol  for  several  days,  but  only  a few 
extremely  minute  granules  of  matter  were  precipitated 
on  the  walls  of  the  cells  ; and  these  were  much  smaller 
and  fewer  than  those  precipitated  on  the  cell-walls  of 
the  rhizomes  and  bladders.  We  may  therefore  con- 


UTRICULAEIA  MONTANA. 


Chap.  XVIII 


440 

elude  that  the  tubers  do  not  serve  as  reservoirs  for 
food,  but  for  water  during  the  dry  season  to  which  the 
plant  is  probably  exposed.  The  many  little  bladders 
filled  with  water  would  aid  towards  the  same  end. 

To  test  the  correctness  of  this  view,  a small  plant, 
growing  in  light  peaty  earth  in  a pot  (only  4^  by  4a 
inches  outside  measure)  was  copiously  watered,  and 
then  kept  without  a drop  of  water  in  the  hothouse. 
Two  of  the  upper  tubers  were  beforehand  uncovered 
and  measured,  and  then  loosely  covered  up  again.  In 
a fortnight’s  time  the  earth  in  the  pot  appeared  ex- 
tremely dry ; but  not  until  the  thirty-fifth  day  were 
the  leaves  in  the  least  affected;  they  then  became 
slightly  reflexed,  though  still  soft  and  green.  This 
plant,  which  bore  only  ten  tubers,  would  no  doubt 
have  resisted  the  drought  for  even  a longer  time, 
had  I not  previously  removed  three  of  the  tubers 
and  cut  off  several  long  rhizomes.  When,  on  the 
thirty-fifth  day,  the  earth  in  the  pot  was  turned  out, 
it  appeared  as  dry  as  the  dust  on  a road.  All  the 
tubers  had  their  surfaces  much  wrinkled,  instead  of 
being  smooth  and  tense.  They  had  all  shrunk,  but  I 
cannot  say  accurately  how  much ; for  as  they  were  at 
first  symmetrically  oval,  I measured  only  their  length 
and  thickness;  but  they  contracted  in  a transverse 
line  much  more  in  one  direction  than  in  another,  so  as 
to  become  greatly  flattened.  One  of  the  two  tubers 
which  had  been  measured  was  now  three-fourths  of 
its  original  length,  and  two-thirds  of  its  original  thick- 
ness in  the  direction  in  which  it  had  been  measured, 
but  in  another  direction  only  one-third  of  its  former 
thickness.  The  other  tuber  was  one-fourth  shorter,  one- 
eighth  less  thick  in  the  direction  in  which  it  had  been 
measured,  and  only  half  as  thick  in  another  direction. 

A slice  was  cut  from  one  cf  these  shrivelled  tubers 


Chap.  XVIII. 


UTRICULAKIA  NELUMBIFOLIA. 


441 


and  examined.  The  cells  still  contained  much  water 
and  no  air,  but  they  were  more  rounded  or  less  angular 
than  before,  and  their  walls  not  nearly  so  straight ; it 
was  therefore  clear  that  the  cells  had  contracted.  The 
tubers,  as  long  as  they  remain  alive,  have  a strong 
attraction  for  water ; the  shrivelled  one,  from  which  a 
slice  had  been  cut,  was  left  in  water  for  22  hrs.  30  m., 
and  its  surface  became  as  smooth  and  tense  as  it 
originally  was.  On  the  other  hand,  a shrivelled  tuber, 
which  by  some  accident  had  been  separated  from  its 
rhizome,  and  which  appeared  dead,  did  not  swell  in 
the  least,  though  left  for  several  days  in  water. 

With  many  kinds  of  plants,  tubers,  bulbs,  &c.  no 
doubt  serve  in  part  as  reservoirs  for  water,  but  I 
know  of  no  case,  besides  the  present  one,  of  such 
organs  having  been  developed  solely  for  this  purpose. 
Prof.  Oliver  informs  me  that  two  or  three  other  species 
of  Utricularia  are  provided  with  these  appendages; 
and  the  group  containing  them  has  in  consequence 
received  the  name  of  orchidioides.  All  the  other 
species  of  Utricularia,  as  well  as  of  certain  closely 
related  genera,  are  either  aquatic  or  marsh  plants; 
therefore,  on  the  principle  of  nearly  allied  plants 
generally  having  a similar  constitution,  a never  failing 
supply  of  water  would  probably  be  of  great  importance 
to  our  present  species.  We  can  thus  understand  the 
meaning  of  the  development  of  its  tubers,  and  of  their 
number  on  the  same  plant,  amounting  in  one  instance 
to  at  least  twenty. 


Utricularia  nelumbifolia,  amethystina,  grif- 

FITHII,  C.ERULEA,  ORBICULATA,  MULTICAULIS. 

As  I wished  to  ascertain  whether  the  bladders  on 
the  rhizomes  of  other  species  of  Utricularia,  and  of  the 


442 


UTRICUT.ARIA  NELUMBIFOLIA. 


Chap.  XVHL 


species  of  certain  closely  allied  genera,  had  the  same 
essential  structure  as  those  of  Utricularia  montana^  and 
whether  they  captured  prey,  I asked  Prof.  Oliver  to  send 
me  fragments  from  the  herbarium  at  Kew.  He  kindly 
selected  some  of  the  most  distinct  forms,  having  entire 
leaves,  and  believed  to  inhabit  marshy  ground  or 
water.  My  son,  Francis  Darwin,  examined  them,  and 
has  given  me  the  following  observations;  but  it 
should  be  borne  in  mind  that  it  is  extremely  difficult 
to  make  out  the  structure  of  such  minute  and  delicate 
objects  after  they  have  been  dried  and  pressed.* 

Utricularia  nelumhifolia  (Organ  Mountains,  Brazil). — 
The  habitat  of  this  species  is  remarkable.  According 
to  its  discoverer,  Mr.  Gardner,!  it  is  aquatic,  but  is 
only  to  be  found  growing  in  the  water  which  collects 
in  the  bottom  of  the  leaves  of  a large  Tillandsia,  that 
inhabits  abundantly  an  arid  rocky  part  of  the  moun- 
tain, at  an  elevation  of  about  5000  feet  above  the  level 
of  the  sea.  Besides  the  ordinary  method  by  seed.it 
propagates  itself  by  runners,  which  it  throws  out  from 
the  base  of  the  flower-stem ; this  runner  is  always 
found  directing  itself  towards  the  nearest  Tillandsia, 
when  it  inserts  its  point  into  the  water  and  gives 
origin  to  a new  plant,  which  in  its  turn  sends  out 
another  shoot.  In  this  manner  I have  seen  not  less 
than  six  plants  united.”  The  bladders  resemble  those 
of  Utricularia  montana  in  all  essential  respects,  even  to 
the  presence  of  a few  minute  two-armed  glands  on  the 
valve.  Within  one  bladder  there  was  the  remnant  of 
the  abdomen  of  some  larva  or  crustacean  of  large  size, 


* Prof.  Oliver  has  given  (‘  Proc. 
Linn.  Soc.’  vol.  iv.  p.  169)  figures 
of  the  bladders  of  two  South 
American  species,  namely,  XJtri- 
ciilaria  Jamesoniana  and  peltata ; 


but  he  does  not  appear  to  have 
paid  particular  attention  to  these 
organs. 

t ‘Travels  in  the  Interior  of 
Brazil,  1836-11/  p.  527. 


Chap.  XVIIL  UTRICULARIA  AMETHYSTINA.  443 

having  a brush  of  long  sharp  bristles  at  the  apex. 
Other  bladders  included  fragments  of  articulate  ani- 
mals, and  many  of  them  contained  broken  pieces  of  a 
curious  organism,  the  nature  of  which  was  not  recog- 
nised by  anyone  to  whom  it  was  shown. 

TJtricularia  amethystina  (Guiana). — This  species  has 
small  entire  leaves,  and  is  apparently  a marsh  plant ; 
but  it  must  grow  in  places  where  crustaceans  exist, 
for  there  were  two  small  species  within  one  of  the 
bladders.  The  bladders  are  nearly  of  the  same  shape 
as  those  of  TJtricularia  montana,  and  are  covered  outside 
with  the  usual  papillae ; but  they  differ  remarkably  in 
the  antennae  being  reduced  to  two  short  points,  united 
by  a membrane  hollowed  out  in  the  middle.  This 
membrane  is  covered  with  innumerable  oblong  glands 
supported  on  long  footstalks;  most  of  which  are 
arranged  in  two  rows  converging  towards  the  valve. 
Some,  however,  are  seated  on  the  margins  of  the  mem- 
brane; and  the  short  ventral  surface  of  the  bladder, 
between  the  petiole  and  valve,  is  thickly  covered  with 
glands.  Most  of  the  heads  had  fallen  off,  and  the  foot- 
stalks alone  remained ; so  that  the  ventral  surface  and 
the  orifice,  when  viewed  under  a weak  power,  appeared 
as  if  clothed  with  fine  bristles.  The  valve  is  narrow,  and 
bears  a few  almost  sessile  glands.  The  collar  against 
which  the  edge  shuts  is  yellowish,  and  presents  the 
usual  structure.  From  the  large  number  of  glands  on 
the  ventral  surface  and  round  the  orifice,  it  is  probable 
that  this  species  lives  in  very  foul  water,  from  which  it 
absorbs  matter,  as  v/ell  as  from  its  captured  and  decay- 
ing prey. 

TJtricularia  griffithii  (Malay  and  Borneo).  — The 
bladders  are  transparent  and  minute;  one  which  was 
measured  being  only  two  C)f  an  inch  (-711  mm.) 
in  diameter.  The  antennae  are  of  moderate  length,  and 


444  UTRICULARIA  MULTICAXJLIS.  Chap.  XVIIL 

project  straight  forward ; they  are  united  for  a short 
space  at  their  bases  by  a membrane ; and  they  bear  a 
moderate  number  of  bristles  or  hairs,  not  simple  as 
heretofore,  but  surmounted  by  glands.  The  bladders 
also  differ  remarkably  from  those  of  the  previous  species, 
as  within  there  are  no  quadrifid,  only  bifid,  processes. 
In  one  bladder  there  was  a minute  aquatic  larva; 
in  another  the  remains  of  some  articulate  animal; 
and  in  most  of  them  grains  of  sand. 

TJtricularia  cserulea  (India).  — The  bladders  re- 
semble those  of  the  last  species,  both  in  the  general 
character  of  the  antennas  and  in  the  processes  with- 
in being  exclusively  bifid.  They  contained  remnants 
of  entomostracan  crustaceans. 

ZJtricularia  orbiculata  (India). — The  orbicular  leavei, 
and  the  stems  bearing  the  bladders  apparently  float  in 
water.  The  bladders  do  not  differ  much  from  those  oJ 
the  two  last  species.  The  antennae,  which  are  united 
for  a short  distance  at  their  bases,  bear  on  their  outer 
surfaces  and  summits  numerous,  long,  multicellular 
hairs,  surmounted  by  glands.  The  processes  within 
the  bladders  are  quadrifid,  with  the  four  diverging 
arms  of  equal  length.  The  prey  which  they  had 
captured  consisted  of  entomostracan  crustaceans. 

TJtricularia  multicaulis  (Sikkim,  India,  7000  to 
11,000  feet).  — The  bladders,  attached  to  rhizomes, 
are  remarkable  from  the  structure  of  the  antennae. 
These  are  broad,  flattened,  and  of  large  size;  they 
bear  on  their  margins  multicellular  hairs,  surmounted 
by  glands.  Their  bases  are  united  into  a single, 
rather  narrow  pedicel,  and  they  thus  appear  like  a 
great  digitate  expansion  at  one  end  of  the  bladder. 
Internally  the  quadrifid  processes  have  divergent  arms 
of  equal  length.  The  bladders  contained  remnants  of 
articulate  animals. 


Chap.  XVm. 


POLTPOMPHOLYX. 


445 


POLYPOMPHOLYX. 

This  genus,  which  is  confined  to  Western  Australia, 
is  characterised  by  having  a “ quadripartite  calyx.”  In 
other  respects,  as  Prof.  Oliver  remarks,*  “ it  is  quite  a 
Utricularia.” 

Folypomjpholyx  multijida, — The  bladders  are  attached 
in  whorls  round  the  summits  of  stiff  stalks.  The  two 
antennae  are  represented  by  a minute  membranous 
fork,  the  basal  part  of  which  forms  a sort  of  hood  over 
the  orifice.  This  hood  expands  into  two  wings  on  each 
side  of  the  bladder.  A third  wing  or  crest  appears  to 
be  formed  by  the  extension  of  the  dorsal  surface  of  the 
petiole ; but  the  structure  of  these  three  wings  could  not 
be  clearly  made  out,  owing  to  the  state  of  the  speci- 
mens. The  inner  surface  of  the  hood  is  lined  with 
long  simple  hairs,  containing  aggregated  matter,  like 
that  within  the  quadrifid  processes  of  the  previously 
described  species  when  in  contact  with  decayed  ani- 
mals. These  hairs  appear  therefore  to  serve  as  absor- 
bents. A valve  was  seen,  but  its  structure  could  not 
be  determined.  On  the  collar  round  the  valve  there 
are  in  the  place  of  glands  numerous  one-celled  papillse, 
having  very  short  footstalks.  The  quadrifid  processes 
have  divergent  arms  of  equal  length.  Eemains  of 
entomostracan  crustaceans  were  found  within  the 
bladders. 

Polypompholyx  tenella, — The  bladders  are  smaller 
than  those  of  the  last  species,  but  have  the  same 
general  structure.  They  were  full  of  debris,  apparently 
organic,  but  no  remains  of  articulate  animals  could 
be  distinguished. 


• Proc.  Linn.  See.’  vol.  iv.  p.  171. 


446 


GENLISEA  ORNATA. 


Chap.  XVIII. 


Genlisea. 

This  remarkable  genus  is  technically  distinguished 
from  Utricularia,  as  I hear  from  Prof.  Oliver,  by 
having  a five-partite  calyx.  Species  are  found  in 
several  parts  of  the  world,  and  are  said  to  be  herbae 
annuae  paludosaB.” 

Gerdisea  ornata  (Brazil).  — This  species  has  been 
described  and  figured  by  Dr.  Warming,*  who  states 
that  it  bears  two  kinds  of  leaves,  called  by  him 
spathulate  and  utriculiferous.  The  latter  include 
cavities ; and  as  these  differ  much  from  the  bladders  of 
the  foregoing  species,  it  will  be  convenient  to  speak  of 
them  as  utricles.  The  accompanying  figure  (fig.  29) 
of  one  of  the  utriculiferous  leaves,  about  thrice  en- 
larged, will  illustrate  the  following  description  by  my 
son,  which  agrees  in  all  essential  points  with  that 
given  by  Dr.  Warming.  The  utricle  (h)  is  formed 
by  a slight  enlargement  of  the  narrow  blade  of  the 
leaf.  A hollow  neck  (n)^  no  less  than  fifteen  times 
as  long  as  the  utricle  itself,  forms  a passage  from  the 
transverse  slit-like  orifice  (o)  into  the  cavity  of  the 
utricle.  A utricle  which  measured  i^^h 

(•705  mm.)  in  its  longer  diameter  had  a neck 
(10*583  mm.)  in  length,  and  of  an  inch  (*254  mm.) 
in  breadth.  On  each  side  of  the  orifice  there  is  a long 
spiral  arm  or  tube  (a) ; the  structure  of  which  will  be 
best  understood  by  the  following  illustration.  Take  a 
narrow  ribbon  and  wind  it  spirally  round  a thin 
cylinder,  so  that  the  edges  come  into  contact  along  its 
whole  length;  then  pinch  up  the  two  edges  so  as  to 
form  a little  crest,  which  will  of  course  wind  spirally 


* “ Bidrag  til  Kundskaben  om  Lentibulariaceae,”  Copenhagen,  1874 


Chap.  XVIIL  STRUCTURE  OF  THE  LEAVES. 


447 


round  the  cylinder  like  a thread  round  a screw.  If  the 
cylinder  is  now  removed,  we  shall  have  a tube  like  one 
of  the  spiral  arms.  The  two  projecting  edges  are  not 
actually  united,  and  a needle 
can  be  pushed  in  easily  be- 
tween them.  They  are  in- 
deed in  many  places  a little 
separated,  forming  narrow 
entrances  into  the  tube ; 
but  this  may  be  the  result 
of  the  drying  of  the  speci- 
mens. The  lamina  of  which 
the  tube  is  formed  seems 
to  be  a lateral  prolongation 
of  the  lip  of  the  orifice ; 
and  the  spiral  line  between 
the  two  projecting  edges  is 
continuous  with  the  corner 
of  the  orifice.  If  a fine 
bristle  is  pushed  down  one 
of  the  arms,  it  passes  into 
the  top  of  the  hollow  neck. 

Whether  the  arms  are  open 
or  closed  at  their  extre- 
mities could  not  be  deter- 
mined, as  all  the  specimens 
were  broken;  nor  does  it 
appear  that  Dr.  Warming 
ascertained  this  point. 

So  much  for  the  external 
structure.  Internally  the 

lower  part  of  the  utricle  is  covered  with  spherical 
papillae,  formed  of  four  cells  (sometimes  eight  accord- 
ing to  Dr.  Warming),  which  evidently  answer  to  the 
quadrifid  processes  within  the  bladders  of  Utricularia. 

20 


(Genlisea  ornata.) 
Utriculiferous  leaf;  enlarged  about 
three  times. 

I Upper  part  of  lamina  of  leaf. 
b Utricle  or  bladder, 
n Neck  of  utricle. 

0 Orifice. 

a Spirally  wound  arms,  with  their 
ends  broken  off. 


448 


GENLISEA  OKNATA. 


Chap.  XVIII. 


These  papillaB  extend  a little  way  up  the  dorsal  and 
ventral  surfaces  of  the  utricle ; and  a few,  according  to 
Warming,  may  be  found  in  the  upper  part.  This 
upper  region  is  covered  by  many  transverse  rows,  one 
above  the  other,  of  short,  closely  approximate  hairs, 
pointing  downwards.  These  hairs  have  broad  bases, 

and  their  tips  are  formed 
by  a separate  cell.  They 
are  absent  in  the  lower  part 
of  the  utricle  where  the  pa- 
pillao  abound.  The  neck 
is  likewise  lined  throughout 
its  whole  length  with  trans- 
verse rows  of  long,  thin, 
transparent  hairs,  having 
broad^  bulbous  (fig.  30)  bases, 
with  similarly  constructed 
sharp  points.  They  arise 
from  little  projecting  ridges, 
formed  of  rectangular  epi- 
dermic cells.  The  hairs 
vary  a little  in  length, 
but  their  points  generally 
extend  down  to  the  row 
next  below;  so  that  if  the 
neck  is  split  open  and  laid 
flat,  the  inner  surface  re- 
sembles a paper  of  pins, — 
Portion  of  inside  of  neck  leading  the  hairs  representing  the 

nto  the  utricle,  greatly  enlarged,  show-  ^ o 

ing  the  downward  pointed  bristles,  pins,  and  the  little  ti'ansverse 

ridges  representing  the  folds 
of  paper  through  which  the 
pins  are  thrust.  These  rows  of  hairs  are  indicated 
in  the  previous  figure  (29)  by  numerous  transverse 
lines  crossing  the  neck.  The  inside  of  the  neck  is 


Fig.  30. 

{Genlisea  ornata.) 


Chap.  XVIII. 


CAPTURED  PREY. 


449 


also  studded  with  papillae ; those  in  the  lower  part  are 
spherical  and  formed  of  four  cells,  as  in  the  lower  part 
of  the  utricle ; those  in  the  upper  part  are  formed  of 
two  cells,  which  are  much  elongated  downwards  beneath 
their  points  of  attachment.  These  two-celled  papillsG 
apparently  correspond  with  the  bifid  process  in  the 
upper  part  of  the  bladders  of  Utricularia.  The  narrow 
transverse  orifice  (o,  fig.  29)  is  situated  between  the 
bases  of  the  two  spiral  arms.  No  valve  could  be 
detected  here,  nor  was  any  such  structure  seen  by 
Dr.  Warming.  The  lips  of  the  orifice  are  armed  with 
many  short,  thick,  sharply  pointed,  somewhat  incurved 
hairs  or  teeth. 

The  two  projecting  edges  of  the  spirally  wound 
lamina,  forming  the  arms,  are  provided  with  short 
incurved  hairs  or  teeth,  exactly  like  those  on  the 
lips.  These  project  inwards  at  right  angles  to  the 
spiral  line  of  junction  between  the  two  edges.  The 
inner  surface  of  the  lamina  supports  two-celled,  elon- 
gated papill90,  resembling  those  in  the  upper  part  of 
the  neck,  but  differing  slightly  from  them,  according 
to  Warming,  in  their  footstalks  being  formed  by 
prolongations  of  large  epidermic  cells  ; whereas  the 
papill90  within  the  neck  rest  on  small  cells  sunk 
amidst  the  larger  ones.  These  spiral  arms  form  a 
conspicuous  difference  between  the  present  genus 
and  Utricularia. 

Lastly,  there  is  a bundle  of  spiral  vessels  which, 
running  up  the  lower  part  of  the  linear  leaf,  divides 
close  beneath  the  utricle.  One  branch  extends  up  the 
dorsal  and  the  other  up  the  ventral  side  of  both  the 
utricle  and  neck.  Of  these  two  branches,  one  enters 
one  spiral  arm,  and  the  other  branch  the  other  arm. 

The  utricles  contained  much  debris  or  dirty  matter, 
which  seemed  organic,  though  no  distinct  organisms 


450 


GENLISEA  ORNATA. 


Chap.  XVIII 


could  be  recognised.  It  is,  indeed,  scarcely  possible 
that  any  object  could  enter  the  small  orifice  and  pass 
down  the  long  narrow  neck,  except  a living  creature. 
Within  the  necks,  however,  of  some  specimens,  a worm 
with  retracted  horny  jaws,  the  abdomen  of  some 
articulate  animal,  and  specks  of  dirt,  probably  the 
remnants  of  other  minute  creatures,  were  found. 
Many  of  the  papillae  within  both  the  utricles  and 
necks  were  discoloured,  as  if  they  had  absorbed  matter. 

From  this  description  it  is  sufficiently  obvious  how 
Genlisea  secures  its  prey.  Small  animals  entering 
the  narrow  orifice — but  what  induces  them  to  enter  is 
not  known  any  more  than  in  the  case  of  XJtricularia — 
would  find  their  egress  rendered  difficult  by  the  sharp 
incurved  hairs  on  the  lips,  and  as  soon  as  they  passed 
some  way  down  the  neck,  it  would  be  scarcely  possible 
for  them  to  return,  owing  to  the  many  transverse  rows 
of  long,  straight,  downward  pointing  hairs,  together 
with  the  ridges  from  which  these  project.  Such  crea- 
tures would,  therefore,  perish  either  within  the  neck 
or  utricle ; and  the  quadrifid  and  bifid  papillsB  would 
absorb  matter  from  their  decayed  remains.  The 
transverse  rows  of  hairs  are  so  numerous  that  they 
seem  superfluous  merely  for  the  sake  of  preventing 
the  escape  of  prey,  and  as  they  are  thin  and  delicate, 
they  probably  serve  as  additional  absorbents,  in  the 
same  manner  as  the  flexible  bristles  on  the  infolded 
margins  of  the  leaves  of  Aldrovanda.  The  spiral  arms 
no  doubt  act  as  accessory  traps.  Until  fresh  leaves 
are  examined,  it  cannot  be  told  whether  the  line  of 
junction  of  the  spirally  wound  lamina  is  a little  open 
along  its  whole  course,  or  only  in  parts,  but  a small 
creature  which  forced  its  way  into  the  tube  at  any 
point,  would  be  prevented  from  escaping  by  the 
incurved  hairs,  and  would  find  an  open  path  down 


Chap.  XVIII.  GENLISEA  FILIFORMIS.  451 

the  tube  into  the  neck,  and  so  into  the  utricle.  If  the 
creature  perished  within  the  spiral  arms,  its  decaying 
remains  would  be  absorbed  and  utilised  by  the  bifid 
papillae.  AVe  thus  see  that  animals  are  captured  by 
Genlisea,  not  by  means  of  an  elastic  valve,  as  with 
the  foregoing  species,  but  by  a contrivance  resembling 
an  eel-trap,  though  more  complex. 

Genlisea  afrieana  (South  Africa). — Fragments  of  the 
utriculiferous  leaves  of  this  species  exhibited  the 
same  structure  as  those  of  Genlisea  ornata,  A nearly 
perfect  Acarus  was  found  within  the  utricle  or  neck 
of  one  leaf,  but  in  which  of  the  two  was  not  recorded. 

Genlisea  aurea  (Brazil). — A fragment  of  the  neck 
of  a utricle  was  lined  with  transverse  rows  of  hairs, 
and  was  furnished  with  elongated  papillae,  exactly 
like  those  within  the  neck  of  Genlisea  ornata.  It  is 
probable,  therefore,  that  the  whole  utricle  is  similarly 
constructed. 

Genlisea  jiliformis  (Bahia,  Brazil). — Many  leaves 
were  examined  and  none  were  found  provided  with 
utricles,  whereas  such  leaves  were  found  without  diffi- 
culty in  the  three  previous  species.  On  the  other 
hand,  the  rhizomes  bear  bladders  resembling  in  essen- 
tial character  those  on  the  rhizomes  of  Utricularia. 
These  bladders  are  transparent,  and  very  small,  viz. 
only  of  an  inch  (*254  mm.)  in  length.  The 
antennsB  are  not  united  at  their  bases,  and  apparently 
bear  some  long  hairs.  On  the  outside  of  the  bladders 
there  are  only  a few  papillae,  and  internally  very  few 
quadrifid  processes.  These  latter,  however,  are  of  un- 
usually large  size,  relatively  to  the  bladder,  with  the 
four  divergent  arms  of  equal  length.  No  prey  could 
be  seen  within  these  minute  bladders.  As  the  rhizomes 
of  this  species  were  furnished  with  bladders,  those  of 
Genlisea  afrieana,  ornata,  and  aurea  were  carefully 


452 


CONCLUSION. 


Chap.  XVIII. 


examined,  but  none  could  be  found.  What  are  we  to 
infer  from  these  facts?  Did  the  three  species  just 
named,  like  their  close  allies,  the  several  species  of 
Utricularia,  aboriginally  possess  bladders  on  their 
rhizomes,  which  they  afterwards  lost,  acquiring  in 
their  place  utriculiferous  leaves  ? In  support  of  this 
view  it  may  be  urged  that  the  bladders  of  Genlisea 
filiformis  appear  from  their  small  size  and  from  the 
fewness  of  their  quadrifid  processes  to  be  tending 
towards  abortion ; but  why  has  not  this  species 
acquired  utriculiferous  leaves,  like  its  congeners  ? 

Conclusion. — It  has  now  been  shown  that  many 
species  of  Utricularia  and  of  two  closely  allied  genera, 
inhabiting  the  most  distant  parts  of  the  world — 
Europe,  Africa,  India,  the  Malay  Archipelago,  Austra- 
lia, North  and  South  America — are  admirably  adapted 
for  capturing  by  two  methods  small  aquatic  or  terres- 
trial animals,  and  that  they  absorb  the  products  of 
their  decay. 

Ordinary  plants  of  the  higher  classes  procure  the 
requisite  inorganic  elements  from  the  soil  by  means 
of  their  roots,  and  absorb  carbonic  acid  from  the 
atmosphere  by  means  of  their  leaves  and  stems. 
But  we  have  seen  in  a previous  part  of  this  work 
that  there  is  a class  of  plants  which  digest  and 
afterwards  absorb  animal  matter,  namely,  all  the 
Droseracese,  Pinguicula,  and,  as  discovered  by  Dr. 
Hooker,  Nepenthes,  and  to  this  class  other  species 
will  almost  certainly  soon  be  added.  These  plants 
can  dissolve  matter  out  of  certain  vegetable  sub- 
stances, such  as  pollen,  seeds,  and  bits  of  leaves.  No 
doubt  their  glands  likewise  absorb  the  salts  of  am- 
monia brought  to  them  by  the  rain.  It  has  also  been 
shown  that  some  other  plants  can  absorb  ammonia  by 


Chap.  XYIII. 


CONCLUSION. 


453 


their  glandular  hairs;  and  these  will  profit  by  that 
brought  to  them  by  the  rain.  There  is  a second  class 
of  plants  which,  as  we  have  just  seen,  cannot  digest, 
but  absorb  the  products  of  the  decay  of  the  animals 
which  they  capture,  namely,  Utricularia  and  its  close 
allies ; and  from  the  excellent  observations  of  Dr. 
Mellichamp  and  Dr.  Canby,  there  can  scarcely  be  a 
doubt  that  Sarracenia  and  Darlingtonia  may  be  added 
to  this  class,  though  the  fact  can  hardly  be  considered 
as  yet  fully  proved.  There  is  a third  class  of  plants 
which  feed,  as  is  now  generally  admitted,  on  the 
products  of  the  decay  of  vegetable  matter,  such  as 
the  bird’s-nest  orchis  (Neottia),  &c.  Lastly,  there  is 
the  well-known  fourth  class  of  parasites  - (such  as  the 
mistletoe),  which  are  nourished  by  the  juices  of 
living  plants.  Most,  however,  of  the  plants  belonging 
to  these  four  classes  obtain  part  of  their  carbon,  like 
ordinary  species,  from  the  atmosphere.  Such  are  the 
diversified  means,  as  far  as  at  present  known,  by  which 
higher  plants  gain  their  subsistence. 


INDEX 


ABSORPTION. 


A. 

Absorption  by  Dionsea,  295 

by  Drosera,  17 

by  Drosophyllum,  337 

by  Pinguicula,  381 

by  glandular  hairs,  344 

— by  glands  of  Utricularia,  416, 
421 

by  quadrifids  of  Utricularia, 

413,  421 

by  Utricularia  montnna,  437 

Acid,  nature  of,  in  digestive  secre- 
tion of  Drosera,  88 

present  in  digestive  fluid  of 

various  species  of  Drosera,  Dio- 
naea,  Drosophyllum,  and  Pingui- 
cula, 278,  301,  339,  381 
Acids,  various,  action  of,  on  Drosera, 
188 

of  the  acetic  series  replacing 

hydrochloric  in  digestion,  89 

• , arsenious  and  chromic,  action 

on  Drosera,  185 

, diluted,  inducing  negative 

osmose,  197 

Adder’s  poison,  action  on  Drosera, 
206 

Aggregation  of  protoplasm  in  Dro- 
sera, 38 

in  Drosera  induced  by  salts  of 

ammonia,  43 

caused  by  small  doses  of 

carbonate  of  ammonia,  145 

of  protoplasm  in  Drosera,  a 

reflex  action,  242 

—  in  various  species  of 

Drosera,  278 

in  Dionaea,  290,  300 


AMMONIA. 

Aggregation  of  protoplasm  in  Dro* 
sophyllum,  337,  339 

in  Pinguicula,  370,  389 

in  Utricularia,  411,  415, 

429,  430,  436 

Albumen,  digested  by  Drosera,  92 

, liquid,  action  on  Drosera,  79 

Alcohol,  diluted,  action  of,  on  Dro- 
sera, 78,  216 

Aldrovanda  vesiculosa,  321 

, absorption  and  digestion  by, 

325 

, varieties  of,  329 

Algse,  aggregation  in  fronds  of,  65 
Alkalies,  arrest  digestive  process  in 
Drosera,  94 

Aluminium,  salts  of,  action  on 
Drosera,  184 

Ammonia,  amount  of,  in  rain  water, 
172 

, carbonate,  action  on  heated 

leaves  of  Drosera,  69 
, j smallness  of  doses  caus- 
ing aggregation  in  Drosera,  145 

, , its  action  on  Drosera, 

141 

, , vapour  of,  absorbed  by 

glands  of  Drosera,  142 
, , smallness  of  doses  caus- 
ing inflection  in  Drosera,  145, 
168 

, phosphate,  smallness  of  doses 

causing  inflection  in  Drosera, 
153,168 

, , size  of  particles  affecting 

Drosera,  173 

, nitrate,  smallness  of  doses 

causing  inflection  in  Drosera,  148, 
168 

f salts  of,  action  on  Drosera,  136 


456 


IIHDEX. 


A3IM0NIA. 

Ammonia,  salts  of,  their  action 
affected  by  previous  immersion  in 
water  and  various  solutions,  213 

, induce  aggregation  in 

Drosera,  43 

• , various  salts  of,  causing  in- 

flection in  Drosera,  166 

Antimony,  tartrate,  action  on  Dro- 
sera, 185 

Areolar  tissue,  its  digestion  by 
Drosera,  102 

Arsenicus  acid,  action  on  Drosera, 
185 

Atropine,  action  on  Drosera,  204 


B. 

Barium,  salts  of,  action  on  Drosera, 
183 

Bases  of  salts,  preponderant  action 
of,  on  Drosera,  186 
Basis,  fibrous,  of  bone,  its  digestion 
by  Drosera,  108 

Belladonna,  extract  of,  action  on 
Drosera,  84 

Bennett,  Mr.  A.  W.,  on  Drose  a,  2 

, coats  of  pollen-grains  not 

digested  by  insects,  117 
Binz,  on  action  of  quinine  on  white 
blood-corpuscles,  201 

, on  p(dsonous  action  of  quinine 

on  low  organisms,  202 
Bone,  its  digestion  by  Drosera,  105 
Brunton,  Lauder,  on  digestion  of 
gelatine.  111 

, on  the  composition  of  casein, 

115 

, on  the  digestion  of  urea,  124 

, of  chlorophyll,  126 

, of  pepsin,  124 

Byblis,  343 


C. 

Cabbage,  decoction  of,  action  on 
Drosera,  83 

Cadmium  chloride,  action  on  Dro- 
sera, 183 

Caesium,  chloride  of,  action  on 
Drosera,  181 


CUKTIS. 

Calcium,  salts  of,  action  on  Drosera 
182 

Camphor,  action  on  Drosera,  209 
Canby,  Dr.,  on  Dionaea,  301,  310, 
313 

, on  Drosera  filiformis,  281 

Caraway,  oil  of,  action  on  Drosera, 
211 

Carbonic  acid,  action  on  Drosera,  221 

, delays  aggregation  in  Drosera, 

59 

Cartilage,  its  digestion  by  Drosera, 
103 

Casein,  its  digestion  by  Drosera,  114 
Cellulose,  not  digested  by  Drosera, 
125 

Chalk,  precipitated,  causing  inflec- 
tion of  Drosera,  32 
Cheese,  its  digestion  by  Drosera, 
116 

Chitine,  not  digested  by  Drosera, 

124 

Chloroform,  effects  of,  on  Drosera, 
217 

, , on  Dionaea,  304 

Chlorophyll,  grains  of,  in  living 
plants,  digested  by  Drosera,  126 
, pure,  not  digested  by  Drosera, 

125 

Chondrin,  its  digestion  by  Drosera, 
112 

Chromic  acid,  action  on  Drosera, 

185 

Cloves,  oil  of,  action  on  Drosera,  212 
Cobalt  chloride,  action  on  Drosera, 

186 

Cobra  poison,  action  on  Drosera* 
206 

Cohn,  Prof.,  on  Aldrovanda,  321 

, on  contractile  tissues  in  plants 

364 

, on  movements  of  stamens  o 

Compositae,  256 

, on  Utricularia,  395 

Colchicine,  action  on  Drosera,  201 
Copper  chloride,  action  on  Drosera. 
185 

Crystallin,  its  digestion  by  Drosera, 
120 

Curare,  action  on  Drosera,  204 
Curtis,  Dr.,  on  Dionaea,  301 


INDEX. 


457 


DARWIN. 

D. 

Darwin,  Francis,  on  the  effect  of  an 
induced  galvanic  current  on  Dro- 
sera,  37 

, on  the  digestion  of  grains  of 

chlorophyll,  126 

, on  Utricularia,  442 

Delpino,  on  Aldrovanda,  321 

, on  Utricularia,  395 

Dentine,  its  digestion  by  Drosera, 
106 

Digestion  of  various  substances  by 
Diona3a,  301 

by  Drosera,  85 

by  Drosophyllum,  339 

by  Pinguicula,  381 

, origin  of  power  of,  361 

Digitaline,  action  on  Drosera,  203 
Dionsea  muscipula,  small  size  of  j 
roots,  286 

, structure  of  leaves,  287 

■ , sensitiveness  of  filaments, 

289 

, absorption  by,  295 

, secretion  by,  295 

, digestion  by,  301 

, effects  on,  of  chloroform,  304 

, manner  of  capturing  insects, 

305 

, transmission  of  motor  impulse, 

313 

, re-expansion  of  lobes,  318 

Direction  of  inflected  tentacles  of 
Drosera,  243 

Dohrn,  Dr.,  on  rhizocephalous  crus- 
taceans, 357 

Dunders,  Prof.,  small  amount  of 
atropine  affecting  the  iris  of  the 
dog,  172 

Dragonfly  caught  by  Drosera,  2 
Drosera  anglica,  278 

binata,  vel  dichotoma,  281 

capensis,  279 

filiformis,  281 

heterophylla,  284 

intermedia,  279 

Drosera  rotundifolia,  structure  of 
leaves,  4 

• , effects  on,  of  nitrogenous 

fluids,  76 


FIBROUS. 

Drosera  rotundifolia,  effects  of  heat 
on,  66 

, its  power  of  digestion,  85 

, backs  of  leaves  not  sensitive, 

231 

, transmission  of  motor  impulse, 

234 

, general  summary,  262 

spathulata,  280 

Droseracese,  concluding  remarks  cxi, 
355 

, their  sensitiveness, compared 

with  that  of  animals,  366 
Drosophyllum,  structure  of  leaves, 
333 

, secretion  by,  334 

, absorption  by,  337 

, digestion  by,  339 


E. 

Enamel,  its  digestion  by  Drosera, 
106 

Erica  tetralix,  glandular  hairs  of, 
351 

Ether,  effects  of,  on  Drosera,  219 

, , on  Dionaea,  304 

Euphorbia,  process  of  aggregation 
in  roots  of,  63 

Exosmose  from  backs  of  leaves  of 
Drosera,  231 


r. 

Fat  not  digested  by  Drosera,  126 

Fayrer,  Dr.,  on  the  nature  of  cobra 
poison,  206 

, on  the  action  of  cobra  poison 

on  animal  protoplasm,  208 

, on  cobra  poison  paralysing 

nerve  centres,  224 

Ferment,  nature  of,  in  secretion  of 
Drosera,  94,  97 

Fibrin,  its  digestion  by  Drosera,  100 

Fibro-cartilage,  its  digestion  by 
Drosera,  104 

Fibro-elastic  tissue,  not  digested  by 
Drosera,  122 

Fibrous  basis  of  bone,  its  digestion 
by  Drosera,  108 


458 


INDEX, 


FLUIDS.  ♦ 

Fluids,  nitrogenous,  effects  of,  on 
Drosera,  76 

Fouinier,  on  acids  causing  move- 
ments in  stamens  of  Berberis,  196 
Frankland,  Prof.,  on  nature  of  acid 
in  secretion  of  Drosera,  88 


G. 

Galvanism,  current  of,  causing  in- 
flection of  Drosera,  37 

, effects  of,  on  Dionsea,  318 

Gardner,  Mr.,  on  Utricularia  nelum- 
bifolia,  442 

Gelatine,  impure,  action  on  Drosera, 
80 

, pure,  its  digestion  by  Drosera, 

110 

Genlisea  africana,  451 

filiformis,  451 

Genlisea  ornata,  structure  of,  446 

, manner  of  capturing  prey, 

450 

Glandular  hairs,  absorption  by,  344 

, summary  on,  353 

Globulin,  its  digestion  by  Drosera, 
120 

Gluten,  its  digestion  by  Drosera, 
117 

Glycerine,  inducing  aggregation  in 
Drosera,  52 

, action  on  Drosera,  212 

Gold  chloride,  action  on  Drosera, 
184 

Gorup-Besanez  on  the  presence  of  a 
solvent  in  seeds  of  the  vetch,  362 
Grass,  decoction  of,  action  on  Dro- 
sera, 84 

Gray,  Asa,  on  the  Droseraceae,  2 
Greenland,  on  Drosera,  1,  5 
Gum,  action  of,  on  Drosera,  77 
Gun-cotton,  not  digested  by  Dro- 
sera, 125 

H. 

Ha;matin,  its  digestion  by  Drosera, 
121 

Hairs,  glandular,  absorption  by,  344 
^ , summary  on,  353 


LEAVES. 

Heat,  inducing  aggregation  in  Dro- 
sera, 53 

, effect  of,  on  Drosera,  66 

, , on  Dionaea,  294,  3 1 9 

Heckel,  on  state  of  stamens  of  Ber- 
beris after  excitement,  43 
Hofmeister,  on  pressure  arresting 
movements  of  protoplasm,  61 
Holland,  Mr.,  on  Utricularia,  395 
Hooker,  Dr.,  on  carnivorous  plants,  2 
, on  power  of  digestion  by  Ne- 
penthes, 97 

, history  of  observations  on 

Dionaea,  286 

Hydrocyanic  acid,  effects  of,  on 
Dionaea,  305 

Hyoscyamus,  action  on  Drosera,  84, 
206 

L 

Iron  chloride,  action  on  Drosera, 
185 

Isinglass,  solution  of,  action  on 
Drosera,  80 


J. 

J ohnson.  Dr.,  on  movement  of  flower- 
stems  of  Pinguicula,  381 


K, 

Klein,  Dr.,  on  microscopic  character 
of  half  digested  bone,  106 

, on  state  of  half  digested  fibro- 

cartilag^,  104 

, on  size  of  micrococci,  173 

Knight,  Mr.,  on  feeding  Dionaea,  301 
Kossmann,  Dr.,  on  rhizocephalous 
crustaceans,  357 


L. 

Lead  chloride,  action  on  Drosera, 
184 

Leaves  of  Drosera,  backs  of,  not 
sensitive,  231 


INDEX. 


459 


LEGUMIN. 

Logumin,  its  digestion  by  Drosera, 
116 

I^emna,  aggregation  in  leaves  of,  64 
Lime,  carbonate  of,  precipitated, 
causing  inflection  of  Drosera,  32 

, phosphate  of,  its  action  on 

Drosera,  109 

Lithium,  salts  of,  action  on  Drosera, 
181 


Magnesium,  salts  of,  action  on  Dro- 
sera, 182 

Manganese  chloride,  action  on  Dro- 
sera, 185 

Marshall,  Mr.  W.,  on  Pinguicula, 
369 

Means  of  movement  in  Dionaea,  313 

in  Drosera,  254 

Meat,  infusion  of,  causing  aggrega- 
tion in  Drosera,  51 

, , action  on  Drosera,  79 

, its  digestion  by  Drosera,  98 

Mercury  perchloride,  action  on 
Drosera,  183 

Milk,  inducing  aggregation  in  Dro- 
sera, 51 

, action  on  Drosera,  79 

, its  digestion  by  Drosera,  113 

Mirabilis  longiflora,  glandular  hairs 
of,  352 

Moggridge,  Traherne,  on  acids  in- 
juring seeds,  128 
Moore,  Dr.,  on  Pinguicula,  390 
Morphia  acetate,  action  on  Drosera, 
205 

Motor  impulse  in  Drosera,  234,  258 

in  Dionsea,  313 

Movement,  origin  of  power  of,  363 
Movements  of  leaves  of  Pinguicula, 
371 

of  tentacles  of  Drosera,  means 

of,  254 

of  Dionsea,  means  of,  313 

Mucin,  not  digested  by  Drosera, 
122 

Mucus,  action  on  Drosera,  80 
Muller,  Fritz,  on  rhizoceplialous 
crustaceans,  357 


PINGUICULA. 

N. 

Nepenthes,  its  power  of  digestion, 
97 

Nickel  chloride,  action  on  Drosera, 
186 

Nicotiana  tabacum,  glandular  haira, 
of,  352 

Nicotine,  action  on  Drosera,  203 
Nitric  ether,  action  on  Drosera,  220 
Nitschke,  Dr.,  references  to  his 
papers  on  Drosera,  1 

, on  sensitiveness  of  backs  of 

leaves  of  Drosera,  231 
, on  direction  of  inflected  ten- 
tacles in  Drosera,  244 

, on  Aldrovanda,  322 

Nourishment,  various  means  of,  by 
plants,  452 

Nuttall,  Dr.,  on  re-expansion  of 
Dionsea,  318 


0. 

Odour  of  pepsin,  emitted  from  leaves 
of  Drosera,  88 

Oil,  olive,  action  of,  on  Drosera,  78, 
126 

Oliver,  Prof.,  on  Utricularia,  432, 
441-446 


P. 

Papaw,  juice  of,  hastening  putrefac- 
tion, 411 

Particles,  minute  size  of,  causing 
inflection  in  Drosera,  27,  32 
Peas,  decoction  of,  action  on  Dro- 
sera, 82 

Pelargonium  zonale,  glandular  hairs 
of,  350 

Pepsin,  odour  of,  emitted  from  Dro- 
sera leaves,  88 

, not  digested  by  Drosera,  123 

, its  secretion  by  animals  ex- 
cited only  after  absorption,  129 
Peptogenes,  129 
Pinguicula  grandiflora,  390 
lusitanica,  391 


460 


INDEX. 


PINGUICULA. 

Pinguicula  vulgaris,  structure  of 
leaves  and  roots,  368 

, number  of  insects  caught  by, 

369 

, power  of  movement,  371 

, secretion  and  absorption  by, 

c 38i 

digestion  by,  381 

, eftects  of  secretion  on  living 

seeds,  390 

Platinum  chloride,  action  on  Dro- 
sera,  186 

Poison  of  cobra  and  adder,  their 
action  on  Drosera,  206 
Pollen,  its  digestion  by  Drosera, 
117 

Polypompholyx,  structure  of,  445 
Potassium,  salts  of,  inducing  ag- 
gregation in  Drosera,  50 

, , action  on  Drosera,  179 

phosphate,  not  decomposed  by 

Drosera,  180,  187 

Price,  Mr.  John,  on  Utricularia, 
429 

Primula  sinensis,  glandular  hairs 
of,  348 

, number  of  glandular  hairs  of, 

355 

Protoplasm,  aggregation  of,  in  Dro- 
sera, 38 

, , in  Drosera,  caused  by 

small  doses  of  carbonate  of  am- 
monia, 145 

, , in  Drosera,  a reflex 

action,  242 

aggregated,  re-dissolution  of, 

53 

, aggregation  of,  in  various 

species  of  Drosera,  278 

, in  Dionaea,  290,  300 

, , in  Drosophyllum,  337, 

339 

, , in  Pinguicula,  370,  389 

, , in  Utricularia,  411,  415, 

429,  430,  436 


Q. 

Quinine,  salts  of,  action  on  Drosera, 
201 


SAXIFKAGA. 


R- 

Rain-water,  amount  of  ammonia  in, 
172 

Ralfs,  Mr.,  on  Pinguicula,  390 
Ransom,  Dr.,  action  of  poisons  on 
the  yolk  of  eggs,  225 
Re-expansion  of  headless  tentacles 
of  Drosera,  229 

of  tentacles  of  Drosera,  260 

of  Dionaea,  318 

Roots  of  Drosera,  18 
— of  Drosera,  process  of  aggrega- 
tion in,  63 

of  Drosera,  absorb  carbonate  of 

ammonia,  141 

of  Dionaea,  286 

of  Drosophyllum,  332 

of  Pinguicula,  369 

Roridula,  342 

Rubidium  chloride,  action  on  Dro- 
sera, 181 


S. 

Sachs,  Prof,  effects  of  heat  on  pro- 
toplasm, 66,  70 

, on  the  dissolution  of  proteid 

compounds  in  the  tissues  of 
plants,  362 

Saliva,  action  on  Drosera,  80 
Salts  and  acids,  various,  effects  of, 
on  subsequent  action  of  ammonia, 
214 

Sanderson,  Burdon,  on  coagulation 
of  albumen  from  heat,  74 
, on  acids  replacing  hydro- 
chloric in  digestion,  89 

, on  the  digestion  of  fibrous 

basis  of  bone,  108 

, of  gluten,  118 

', of  globulin,  120 

, of  chlorophyll,  126 

, on  different  effect  of  sodium 

and  potassium  on  animals,  187 

, on  electric  currents  in  Dionaea, 

318  ^ 

Saxifraga  umbrosa,  glandular  haira 
of,  345 


INDEX. 


461 


scmFP. 


TURPENTINE. 


Schiff,  on  hydrochloric  acid  dis- 
solving coagulated  albumen, 
86 

, on  manner  of  digestion  of 

albumen,  93 

, on  changes  in  meat  during 

digestion,  99 

, on  the  coagulation  of  milk, 

lU 

, on  the  digestion  of  casein, 

116 

— — , of  mucus,  123 

, on  peptogenes,  129 

Schloesing,  on  absorption  of  nitro- 
gen by  Nicotiana,  352 
Scott,  Mr.,  on  Drosera,  1 
Secretion  of  Drosera,  general  ac- 
count of,  13 

■  , its  antiseptic  power, 

15 

•  , becomes  acid  from  ex- 

citement, 86 

■  , nature  of  its  ferment, 

94,  97 

■  by  Dion  sea,  295 

by  Drosophyllum,  335 

•  by  Pinguicula,  381 

Seeds,  living,  acted  on  by  Drosera, 
127 

• — — , , acted  on  by  Pinguicula, 

385,  390 

Sensitiveness,  localisation  of,  in 
Drosera,  229 

of  Dionsea,  289 

of  Pinguicula,  371 

Silver  nitrate,  action  on  Drosera, 
181 

Sodium,  salts  of,  action  on  Drosera, 
176 

, , inducing  aggregation  in 

Drosera,  50 

Sondera  heterophylla,  284 
Sorby,  Mr.,  on  colouring  matter  of 
Drosera,  5 

Spectroscope,  its  power  compared 
with  that  of  Drosera,  170 
Starch,  action  of,  on  Drosera,  78, 
126 

Stein,  on  Aldrovanda,  321 
Strontium,  salts  of,  action  on  Dro- 
sera, 183 


Strychnine,  salts  of,  action  on 
Drosera,  199 

Sugar,  solution  of,  action  of,  on 
Drosera,  78 

, , inducing  aggregation  in 

Drosera,  51 
Sulphuric 
219 


Tait,  Mr.,  on 
Taylor,  Alfred, 
minute  doses  of  poisons. 

Tea,  infusion  of,  action  on  Drosera, 


78 


Tentacles  of  Drosera,  move  when 
glands  cut  of,  36,  229 

, inflection,  direction  of,  243 

, means  of  movement,  254 

, re-expansion  of,  260 

Theine,  action  on  Drosera,  204 
Tin  chloride,  action  on  Drosera, 
185 

Tissue,  areolar,  its  digestion  by 
Drosera,  102 

, fibro-elastic,  not  digested  by 

Drosera,  122 

Tissues  through  which  impulse  is 
transmitted  in  Drosera,  247 

ill  Dionsea,  313 

Touches  repeated,  causing  inflec- 
tion in  Drosera,  34 
Transmission  of  motor  impulse  in 
Drosera,  234 

in  Dionsea,  313 

Traube,  Dr.,  on  artificial  cells,  216 
Treat,  Mrs.,  on  Drosera  filiformis, 
281 


, on  Dionsea,  311 

— — , on  Utricularia,  408,  430 
Trecul,  on  Drosera,  1, 5 
Tubers  of  Utricularia  montana,  439 
* Turpentine,  action  on  Drosera,  212 


462 


INDEX, 


UBEA. 


Urea,  not  digested  by  Drosera,  124 
Urine,  action  on  Drosera,  79 
Utricularia  clandestina,  430 
minor,  429 

|"triicularia  montana,  structure  of 
bladders,  431 

, animals  caught  by,  435 

, absorption  by,  437 

, tubers  of,  serving  as  reservoirs, 

439 

Utricularia  neglecta,  structure  of 
bladders,  397 

, animals  caught  by,  405 

, absorption  by,  413 

, summary  on  absorption,  421 

, development  of  bladders,  424 

Utricularia,  various  species  of,  441 
Utricularia  vulgaris,  428 


V. 

Veratrine,  action  on  Drosera,  204 
Vessels  in  leaves  of  Drosera,  247 

of  Dionsea,  314 

Vogel,  on  effects  of  camphor  on 
plants,  209 


ZINC. 

W. 

Warming,  Dr.,  on  Drosera,  2,  6 

, on  roots  of  Utricularia,  397 

, on  trichomes,  359 

, on  Genlisea,  446 

, on  parenchymatous  cells  in 

tentacles  of  Drosera,  252 
Water,  drops  of,  not  causing  inflec- 
tion in  Drosera,  35 
, its  power  in  causing  aggrega- 
tion in  Drosera,  52 

, its  power  in  causing  inflection 

in  Drosera,  139 

and  various  solutions,  effects 

of,  on  subsequent  action  of  am- 
monia, 213 

Wilkinson,  Rev.,  on  Utricularia, 
398 


Z 

Ziegler,  his  statements  with  respect 
to  Drosera,  23 

, experiments  by  cutting  ves- 
sels of  Drosera,  249 
Zinc  chloride,  action  on  Drosera, 
184 


r/u.A,.. 


/ 


3 0112  099088418 


